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IC 9132 



Bureau of Mines Information Circular/1987 



A Statistical Analysis of Metal and Nonmetal 
Mine Fire Incidents in the United States 
From 1950 to 1984 



By Shail J. Butani and William H. Pomroy 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9132 



A Statistical Analysis of Metal and Nonmetal 
Mine Fire Incidents in the United States 
From 1950 to 1984 



By Shail J. Butani and William H. Pomroy 




UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 










Library of Congress Cataloging in Publication Data: 



Butani, Shail J. 

A statistical analysis of metal and nonmetal mine fire incidents in 
the United States from 1950 to 1984. 

(Information circular/United States Department of the Interior, Bureau of Mines; 9132) 

Includes bibliographical references. 

Supt. of Docs, no.: I 28.27: 9132. 

1. Mine fires — United States — Statistics. 2. Mine fires — United States — Statistical 
methods. I. Pomroy, William H. II. Title. III. Series: Information circular (United States. 
Bureau of Mines); 9132. 



T«29SrrJ4— [TN3151 363.379 



86-600299 



CONTENTS 

Page 

Abstract 1 

Introduction 2 

Data analysis methods 2 

Chi-square 3 

t-test 4 

Spearman rank order correlation 6 

Levels of significance and rounding 7 

Incidence rate 7 

Reported fires 7 

Underground fires 8 

Time trends 8 

Ore type 11 

Ignition source 12 

Burning substance 13 

Location 15 

Equipment involved 17 

Means of detection 18 

Duration 18 

Number of injuries 19 

Number of deaths 21 

Mining method 21 

Successful extinguishing agent 22 

Surface fires at surface and underground mines 23 

Time trends 23 

Ore type 26 

Ignition source 27 

Burning substance 27 

Location 28 

Equipment involved 28 

Means of detection 29 

Duration 29 

Number of injuries 30 

Number of deaths 30 

Successful extinguishing agent 31 

Comparison of underground and surface fires 32 

Time trends 32 

Ore type 32 

Ignition source 32 

Burning substance 32 

Location 32 

Equipment involved 32 

Means of detection 32 

Duration 33 

Number of injuries 33 

Number of deaths 33 

Successful extinguishing agent 34 

Nonreportable fires 34 

Underground fires 36 

Ingition source 36 

Burning substance 36 

Location 36 



ii 



CONTENTS— Continued 

Page 

Equipment involved 36 

Successful extinguishing agent 36 

Surface fires 36 

Ignition source 36 

Burning substance 36 

Location 36 

Equipment involved 36 

Successful extinguishing agent 36 

Opinion data from mine safety directors 36 

Underground mine fires 37 

Surface mine fires 37 

Summary of opinion data 37 

Summary 38 

Ignition source 38 

Burning substance 39 

Location 39 

Equipment involved 39 

Successful extinguishing agent 39 

Conclusions 40 

Appendix 41 

ILLUSTRATIONS 

1. Underground fire incidents by year, 1950-84 8 

2. Average number of fire incidents per year, underground versus surface, 

during three time periods 10 

3. Fire incidence rates by year, underground versus surface, 1978-84 11 

4. Average underground fire incidence rates by ore type, 1978-84 13 

5. Surface fire incidents by year, 1950-84 24 

6. Average surface fire incidence rates by ore type, 1978-84 27 

7. Percentage of mobile equipment fires, underground versus surface, during 

three time periods 33 

8. Percentage of fires detected immediately, underground versus surface, 

during three time periods 34 

TABLES 

1. Reported underground fire incidents by year 6 

2. Ranking of reported underground fire incidents by year 7 

3. Number of reportd underground fire incidents by three time periods 9 

4. Reported underground fire incidence rates, 1978-84 10 

5. Reported underground fires by principal ore, three time periods 12 

6. Average reported underground fire incidence rates by ore, 1978-84 12 

7. Reported underground fires by ignition source, three time periods 14 

8. Reported underground fires by burning substance, three time periods 14 

9. Reported underground fires by location, three time periods 15 

10. Reported underground electrical fires by location, three time periods 16 



TABLE S — Con t inued 



iii 



Page 



11. Reported underground welding or cutting fires by location, three time 

periods 16 

12. Reported underground fires by equipment involved, three time periods 17 

13. Reported underground electrical fires by equipment, three time periods.... 18 

14. Reported underground fires by means of detection, three time periods 18 

15. Reported underground fires by duration, three time periods 19 

16. Reported underground fires by ignition source and duration, two time 

periods 20 

17. Reported underground fires by number of injuries, three time periods 20 

18. Reported underground injury fires by ignition source, three time periods.. 20 

19. Reported underground injury fires by location, three time periods 21 

20. Reported underground injury fires by equipment, three time periods 21 

21. Reported underground fires by number of deaths, three time periods 21 

22. Reported underground fires by mining method, three time periods 22 

23. Reported underground fires by successful extinguishing agent, three time 

periods 22 

24. Reported underground fires, joint distribution of successful extinguishing 

agents , by three time periods 23 

25. Reported surface fire incidents by year 23 

26. Ranking of reported surface fire incidents by year 25 

27. Number of reported surface fire incidents by three time periods 25 

28. Reported surface fire incidence rates, 1978-84 25 

29. Reported surface fires by principal ore, three time periods 26 

30. Average reported surface fire incidence rates by ore, 1978-84 26 

31. Reported surface fires by ignition source, three time periods 28 

32. Reported surface fires by burning substance, three time periods 28 

33. Reported surface fires by location, three time periods 29 

34. Reported surface fires by equipment involved, three time periods 29 

35. Reported surface fires by means of detection, three time periods 30 

36. Reported surface fires by duration, three time periods 30 

37. Reported surface fires by number of injuries, three time periods 31 

38. Reported surface fires by number of deaths, three time periods 31 

39. Reported surface fires by successful extinguishing agent, three time 

periods 31 

40. Nonreportable underground fires 35 

41. Nonreportable surface fires 35 

42. Average rankings of opinion data for ignition source, burning substance, 

and successful extinguishing agent, underground fires 37 

43. Average rankings of opinion data for ignition source, burning substance, 

and successful extinguishing agent, surface fires 37 

44. Major study findings of reported fires 38 

45. Major study findings of nonreportable fires 39 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS 


REPORT 


h hour pet 


percent 


min minute yr 


year 



A Statistical Analysis of Metal and Nonmetal 

Mine Fire Incidents in the United States 

From 1950 to 1984 



By Shail J. Butani' and William H. Pomroy 2 



ABSTRACT 

This Bureau of Mines publication presents a statistical analysis of 
official U.S. Mine Safety and Health Administration (MSHA) metal and 
nonmetal mine fire reports from 1950 through 1984, plus accounts of se- 
lected nonreportable fires (less than 30 min and no injury) and opinion 
data on fire hazards from mine safety directors. Fires were analyzed by 
time trends, ore type, ignition source, burning substance, location in 
mine, equipment involved, means of detection, duration, number of injur- 
ies and fatalities, mining method, and successful extinguishing agent. 

The leading ignition sources were electricity in underground fires and 
engine heat in reported surface fires. The most frequent burning sub- 
stance was combustible liquids for all nonreportable fires, reported 
surface fires, and reported underground fires from 1978 to 1984. For 
underground fires reported prior to 1978, timber was the leading burning 
substance. Mobile equipment was the type most frequently involved in 
both underground and surface fires. Underground fires occurred most of- 
ten in haulageway or drift areas, and reported surface fires occurred 
most often in plant and mill buildings, while most nonreportable surface 
fires occurred in other areas. The most common methods of extinguish- 
ment were water hose lines for reported fires and dry chemical hand- 
portable extinguishers for nonreportable fires. 



' Mathematical statistician. 
■^ Supervisory mining engineer. 
Twin Cities Research Center, Bureau of Mines, Minneapolis, MN. 



INTRODUCTION 



In support of the Bureau of Mines re- 
search on mine fire protection, two sep- 
arate baseline studies on mine fire in- 
cidents have been prepared. The first 
study addressed coal mine fires. The re- 
sults of that study are summarized in the 
Bureau's Information Circular 8830, "A 
Statistical Analysis of Coal Mine Fire 
Incidents in the United States From 1950 
to 1977." This second report, address- 
ing metal and nonmetal mine fires, is the 
companion to IC 8830. Together, these 
two reports provide a comprehensive, fac- 
tual summary of the mining industry's 
fire experience. 

This report, like IC 8830, covers 
(1) MSHA fire incident reports, (2) rec- 
ords of nonreportable fires (less than 30 
min and no injury), and (3) mine safety 
directors' opinions on fire hazards. The 
MSHA fire reports provide the most reli- 
able, objective, and accurate historcial 
record of the major noncoal mine fires 
that occurred during the study period 
(1950 through 1984). However, MSHA fire 
reports alone understate the true magni- 
tude of the fire problem because metal 
and nonmetal mines have been legally re- 
quired to report fires to MSHA only since 
1968. Although some fires were reported 
prior to 1968, doubtless a great many 
were not. Also, the reporting regu- 
lations that took effect in 1968 spe- 
cify that only fires lasting 30 min or 
longer or involving an injury need to be 



reported. MSHA fire reports are thus 
limited in scope by MSHA's legal author- 
ity. In order to provide a more compre- 
hensive data base, it was also necessary 
to gather and analyze mine company rec- 
ords of nonreportable fires. 

Finally, since mine fires are relative- 
ly rare events, it is desirable to ana- 
lyze not only the fires themselves, but 
also the "near-misses" (which occur much 
more frequently) and the unsafe condi- 
tions that could give rise to future 
fires. Thus, opinion data from mine 
safety directors were collected and sep- 
arately analyzed in an effort to broaden 
the discussion and to characterize and 
rank mine fire hazards in general. The 
1950 to 1977 data were collected via a 
research and development contract with 
Allen Corp. of America. These data have 
been previously published in the form of 
a Bureau Open File Report and are avail- 
able from the National Technical Informa- 
tion Service (NTIS). 3 The 1978 through 
1984 data have not been previously pub- 
lished. The reported mine fire data have 
also been formatted and entered into a 
computer data base using the Lotus 1-2-3 
software 4 for IBM-compatible personal 
computers. Use of this computer data 
base would greatly simplify the analysis 
of metal and nonmetal mine fires for the 
specialized purposes of individual users. 
Microdata are also available from the au- 
thors on hard copy. 



DATA ANALYSIS METHODS 



Three statistical techniques were em- 
ployed to analyze the data collected: 
the chi-square test, the t-test, and 
the Spearman rank order correlation. A 



3 Baker, R. M., J 
and J. Wishmyer. 
raphy of Metal and 
ports (contract JO 
America) . Volume 
81 , 1980, 64 pp. 
Volume II. BuMine 
284 pp.; NTIS PB 
BuMines OFR 68(3)- 
PB 81-223745. 



. Nagy, L. B. McDonald, 

An Annotated Bibliog- 

Nonmetal Mine Fire Re- 

295035, Allen Corp. of 

I. BuMines OFR 68(1)- 

; NTIS PB 81-223729. 

s OFR 68(2)-81 , 1980, 

81-223737. Appendix. 

1 , 1980, 390 pp.; NTIS 



detailed discussion of these methods can 
be found in basic statistical books. 5 
Additionally, incidence rates were com- 
puted where possible. Each of these 
methods of analysis is discussed below. 

^Reference to specific products does 
not imply endorsement by the Bureau of 
Mines . 

5 Mendenhall, W. Introduction to Sta- 
tistics. Wadsworth Publ. Co., Inc., 
1965, 305 pp. 

Siegel, S. Nonparametric Statistics 
for the Behavioral Sciences. McGraw- 
Hill, 1956, 312 pp. 



CHI- SQUARE 

Chi-square (x 2 )» as an analysis tech- 
nique, is used in situations requiring 
comparison of an observed number of re- 
sponses in each of certain chosen cate- 
gories with an expected number, which is 
based on the null hypothesis (see discus- 
sion of null hypothesis below). The ob- 
served values or frequencies are those 
obtained by direct observation or by tab- 
ulation of the various types of data. 
The expected or theoretical frequencies 
are generated on the basis of some under- 
lying assumption (the null hypothesis), 
independent of the observed data. The 
computational formula for chi-square val- 
ues is 



,2 _ 



= I 



(0, - E,) 2 



i=l 



where K = number of categories , 



1 = observed number of cases in 
i* h category, 



difference is said to be significant. 
Thus, the null hypothesis concerning the 
theoretical frequencies is rejected; that 
is, the differences between the observed 
and expected frequencies are greater than 
would be expected to exist by chance. 

Throughout this report, the null hy- 
pothesis used for analyzing data within a 
time period is that an equal number of 
fires are expected for all categories 
within each factor studied — ore type, 
ignition source, location, etc. As an 
example, refer to the tabulation below, 
which shows reported underground fires by 
ignition source, 1968-77: 6 



Electrical 

Welding sparks or hot slag 

Engine heat 

Spontaneous combustion. . . . 

Friction 

Explosives 

Other 

Total 



Number 


Pet 


39 


46.4 


16 


19.0 


7 


8.3 


13 


15.5 


6 


7.1 


1 


1.2 


2 


2.4 



84 



100.0 



and 



E| 



K 

I 
i=l 



= expected number of cases in 
i +h category under the null 
hypothesis, 

directs one to sum over all 
categories. 



That is, chi-square equals the summa- 
tion of the squared value of the differ- 
ence of observed and expected values 
divided by the corresponding expected 
value. 

Tf the agreement between the observed 
and expected frequencies is close, the 
differences (Oi - Ej) will be small, and 
consequently, chi-square will be small. 
On the other hand, if the differences are 
large, the value of chi-square will also 
be large. The larger chi-square is, the 
more likely it is that the observed 
values did not come from the population 
on which the null hypothesis is based. 
If the computed value of chi-square is 
greater than the tabled value of chi- 
square for a specified significance level 
(oc; usually a = 0.05 or 0.01) with K — \ 
degrees of freedom (d.f.), then the 



According to the above-stated hypothesis, 
all types of ignition sources would be 
expected to have caused an equal or near- 
ly equal number of fires. Thus, the ex- 
pected frequency for each ignition source 
type would be the average frequency of 



all ignition source types specified , 
this case, the expected value is 



In 



39+16+7+13+6+1+2 
K = 7 



= 12.0, 



where K = number of different types of 
ignition sources. 

Thus, the computation of chi-square is as 
follows: 



2 _ (39 - 12. 0) 2 (16 - 12.0) 
* 12 12 



+ • • . + -r-z — 85.67. 



6 Data from table 7, which appears later 
in this report. 



The tabled value of chl-square with 6 
(K - 1) d.f. at a = 0.01 is 16.81. Since 
the computed value of chi-square (85.67) 
is greater than the tabled value of chi- 
square (16.81), the null hypothesis is 
rejected. This implies that all ignition 
source types are not equally involved in 
metal and nonmetal underground fires for 
the period 1968-77. 

When the expected frequencies are small 
(less than five), the chi-square test is 
generally not valid. Also, the chi- 
square test is not appropriate for the 
actual number of fires across time peri- 
ods, because the reporting requirements 
before 1968 were less stringent and, con- 
sequently, a number of fires were not 
reported pre-1968. Hence, the underlying 
assumption of an equal number of fires 
per year is not met. Therefore, the chi- 
square test is not applied across all 
situations; instead, the t-test, con- 
cerning proportions (probabilities), is 
used. 

t-TEST 

The first type of t-test is for the 
one-sample case; it is concerned with de- 
termining whether the proportion of ob- 
served fires in a category within a time 
period is more than what is expected un- 
der the null hypothesis (that all catego- 
ries have the same proportion of fires). 
Only probabilities that are greater than 
what is expected are analyzed, because 
the concern is for those categories that 
are hazardous. The computational formula 
for the t-test is 



Po 



Pod - Po) 



t = 



where p = observed proportion of acci- 
dents falling in the cate- 
gory of interest, 

p = proportion of accidents ex- 
pected under the null hy- 
pothesis (in this report, p 
= 1.00 divided by the number 
of categories) , 



and n = total number of specified fires 
within a time period. 

A comparison is made between the calcu- 
lated value of t and the tabled value of 
t; the tabled value of t with its associ- 
ated d.f. (n - 1) is such that the area 
under the distribution curve to the right 
of t a is equal to n, the significance 
level. If the calculated value of t is 
greater than the tabled value of t, the 
difference is said to be significant and 
not merely due to chance. Consequently, 
the null hypothesis is rejected in favor 
of the alternative hypothesis; namely, 
the category has proportionately more 
fires than what is expected. As an ex- 
ample, refer to the tabulation below, 
which shows reported underground electri- 
cal fires by location, 1950-67: 7 



Number 



Haulageway-drif t 

Substation-shop-storage- 
pump 

Shaft-raise-winze 

Working face 

Mined-out waste 

Other 

Total 



Pet 



31.8 



4 


18.2 


7 


31.8 


2 


9.1 


I 


4.5 


1 


4.5 



22 



100.0 



The null hypothesis is tested, that 
the probability of electrical fires in 
haulageway-drif t locations is equal to 
0.167 (1.00 divided by the number of 
categories) . 

t = P ~ Po 



J P( 


>0 - 


- Po) 


V 

0. 


n 

,318 


- 0.167 


10. 


167 


(0.833) 



22 



= 1.91. 



The tabled value of t with 21 d.f. at 
the 0.05 significance level is 1.72. 
Since the computed value is greater than 

^Data from table 10, which appears lat- 
er in this report. 



the tabled value, the null hypothesis is 
rejected; that is, the relative frequency 
of the haulageway-drif t location as the 
site of electrical fires is significantly 
more than its share of one out of every 
six fires. 

The absolute t-values ( 1 1 1 ) for the 
one-sample case, where applicable, are 
shown at the bottom of the tables, under 
the appropriate time periods. 

The second type of t-test concerns the 
difference between two proportions. This 
test determines whether the observed dif- 
ference between proportions from the two 
samples is a real difference or is due to 
random variation. The null hypothesis in 
this test is Pj = P2, where Pj, and P2 
are the proportion of cases in population 
1 and population 2, respectively, pos- 
sessing a certain attribute that is of 
interest. The computational formula for 
this test is 



t = 



Pi ~ P2 



^-»(k + k) 



where pi = number of cases in sample 1 
possessing a certain attri- 
bute, divided by ni, 

P2 = number of cases in sample 2 
possessing a certain attri- 
bute, divided by n2, 

rij = sample size drawn from popu- 
lation 1, 

n2 = sample size drawn from popu- 
lation 2, 



and 



n lPl + n 2P2 
ni + n2 



A comparison is then made between the 
absolute calculated value of t and the 
tabled value of t. As before, the tabled 
value of t with its associated d.f. (nj^ 
+ n2 - 2) is such that the area under the 
distribution curve to the right of t a is 
equal to a, the significance level. The 
absolute value of t is compared to the 



tabled value because the alternative 
hypothesis is that either Pj is greater 
than P2 or P2 is greater than Pj. Again, 
if the absolute calculated value of t is 
greater than the tabled value of t, then 
the difference between the two propor- 
tions is significant and not merely due 
to chance. Consequently, the null hy- 
pothesis that the two probabilities are 
equal is rejected in favor of one proba- 
bility being greater than the other. 

The following data can be used to test 
the hypothesis that the proportion of un- 
derground electrical fires located in 
haulageway-drif t locations in 1950 to 
1967 is equal to the proportion in 1968 
to 1977. Reported underground electrical 
fires by location, two time periods: 8 

Period I Period II 



1950-67 



1968-77 



No. 



Pet 



No. 



Haulageway-drif t. 7 31.8 18 
Substation-shop- 
storage-pump. .. . 4 18.2 13 
Shaft-raise-winze 7 31.8 3 

Working face 2 9.1 4 

Mined-out waste.. 1 4.5 

Other _J_ 4.5 1 

Total 22 100.0 39 



Pet 



46.2 



33, 


.3 


7, 


.7 


10, 


.3 




.0 


2, 


.6 



100.0 



t = 



Pi - P2 



>>-»>(^) 



where pi = y~- = 0.318, 

1 q 
P2 =3! = 0.462, 

ni = 22, 

n 2 = 39, 

22 (0.318) + 39 (0.462) 



and 



22 + 39 



= 0.410. 



8 Data from table 10. 



0.318 - 0.461 



J 



(0.410) (0.590) 



_T 

22 



1 

39 



|t| = 1.09. 



The absolute calculated value of t = 1.09 
is less than the tabled value of t 
= 1.645 (with 59 d.f. and a = 0.05), so 
the null hypothesis cannot be rejected. 
That is, the difference between the two 
proportions could be due to random 
variation. 

The absolute t-values for the two- 
sample case, where applicable, are given 
in the last two columns of the tables. 

SPEARMAN RANK ORDER CORRELATION 

The Spearman rank order correlation 
(r s ) is a measure of concordance or 
agreement, the tendency of two ranks to 
be similar. This test was chosen as the 
measure of correlation because it is non- 
parametric — it makes no assumption about 
the shape of the distribution curve of 
the underlying population. It was also 
chosen because both variables can be mea- 
sured in at least an ordinal scale so 
that the objects or individuals under 
study may be ranked in two ordered 



series. For example, using the data in 
table 1, the number of fires, denoted as 
Xj, X2, ... Xn, and the year, denoted as 
Yj, Y2, ... Yn, may be ranked as shown 
in table 2. Rank correlation may then be 
used to determine the relation between 
the X's and Y's. The formula used in 
calculating the Spearman rank order 
correlation is as follows: 



= 1 - 



N 
6 I d 



N(N 2 - 1) 



where d| = Xj - Y| 

and N = total number of observations. 

The value of r s is always equal to or 
greater than -1.0 and equal to or less 
than 1.0; that is, -1.0 < r s < 1.0. If 
the computed value of r s exceeds the ta- 
bled value based on N and a (significance 
level) , then the rank order correlation 
is said to be significant; that is, the 
agreement between the two sets of ranks 
is greater than would be expected to oc- 
cur by chance. 

Using the ranked tabulated data in ta- 
ble 2 as an example, the Spearman rank 
order correlation would be 



= 1-6 



(3 



l) 2 + (18.5 - 2) 2 + ... + (23.0 - 34) 2 + (20.5 - 35) 2 ] 



35 [(35) 2 - 1] 



= 0.569 



For N = 35 and a = 0.01, the tabled value 
of r s is 0.432. Since the computed value 
of r s is greater than the tabled value, 



the rank order correlation 
significant. 



is said to be 



TABLE 1. - Reported underground fire incidents by year 



Year 



1950.. 


1951.. 


1952.. 


1953.. 


1954.. 


1955.. 


1956.. 


1957.. 


1958.. 


1959.. 


I960.. 


1961.. 



Number of 
incidents 

1 

5 
3 
3 
2 
4 
6 
10 
2 
7 
3 
3 



Year 



1962. 
1963. 
1964. 
1965. 
1966. 
1967. 
1968. 
1969. 
1970. 
1971. 
1972. 
1973. 



Number of 
incidents 



2 

4 

2 

2 

2 

4 



4 

5 
12 
21 



Year 

1974.. 
1975.. 
1976.. 
1977.. 
1978.. 
1979.. 
1980.. 
1981.. 
1982.. 
1983.. 
1984.. 
Total 



Number of 
incidents 

15 
10 

8 
13 
23 
10 

7 
11 
12 

7 

6 
229 



TABLE 2. - Ranking of reported underground fire incidents by year 



Year 


Number of 
incidents 


Rank 


Year 


Number of 
incidents 


Rank 




Year 


Incidents 


Year 


Incidents 


1950 


1 


1 


3.0 


1968 


4 


19 


15.5 


1951.... 


5 


2 


18.5 


1969 





20 


1.5 


1952 


3 


3 


11.5 


1970 


4 


21 


15.5 


1943 


3 


4 


11.5 


1971 


5 


22 


18.5 


1954 


2 


5 


6.5 


1972 


12 


23 


30.5 


1955 


4 


6 


15.5 


1973 


21 


24 


34.0 


1956.... 


6 


7 


20.5 


1974 


15 


25 


33.0 


1957 


10 


8 


27.0 


1975 


10 


26 


27.0 


1958 


2 


9 


6.5 


1976 


8 


27 


25.0 


1959 


7 


10 


23.0 


1977 


13 


28 


32.0 


1960 


3 


11 


11.5 


1978 


23 


29 


35.0 


1961 


3 


12 


11.5 


1979 


10 


30 


27.0 


1962 





13 


1.5 


1980.... 


7 


31 


23.0 


1963 


2 


14 


6.5 


1981 


11 


32 


29.0 


1964 


4 


15 


15.5 


1982 


12 


33 


30.5 


1965 


2 


16 


6.5 


1983 


7 


34 


23.0 


1966 


2 
2 


17 
18 


6.5 
6.5 


1984 

Total. 


6 


35 


20.5 


1967 


229 


NAp 


NAp 



NAp Not applicable. 



0.569 (significant at 1-pct level) 



LEVELS OF SIGNIFICANCE AND ROUNDING 

Levels of significance are provided in 
tbe tables for all statistical analyses 
reported. Significant results are iden- 
tified by eitber one or two asterisks, 
denoting probabilities of 0.05 and 0.01, 
respectively. Lack of an 
cates tbat tbe results 
cant; tbat is, tbere 
0.05 probability tbat tbe results could 
have occurred by chance. In some cases, 
no test was made, for any one of several 
reasons. These cases are denoted as "not 
determined" (ND). 

The sum of the percentage components in 
the tables may not exactly equal 100.0 
because of rounding. 

INCIDENCE RATE 



asterisk indi- 
were not signifi- 
is a greater than 



incidence rates (IR). Incidence rates 
are used to standardize or normalize the 
number of fires on the basis of exposure 
hours so that meaningful comparisons can 
be made. The incidence rates in this re- 
port represent the number of fires per 
10,000 full-time workers and are calcu- 
lated as 



IR = 



number of fires 
total hours worked 



x 20 million h, 



where 20 million h is equivalent to 
10,000 full-time workers working 40 h per 
week and 50 weeks per year. 

Data from 1980 9 may be used as an exam- 
ple. The incidence rate for 1980 is 



IR 



80 54,200,000 



x 20,000,000; 



The last type of analysis is con- 
cerned with the relative measure based on 



IR 80 " 2 ' 6 ' 



REPORTED FIRES 



For the period 1950-77, MSHA fire re- 
ports were acquired through searches of 
the official files of all MSHA metal- 
nonmetal inspection offices and the head- 
quarters office at Arlington, VA. The 



inspection offices included in the search 
are listed in the appendix. 

^Data from table 4, which appears later 
in the report. 



At each MSHA office, project personnel 
searched through all accident report 
files on fires, explosives, and igni- 
tions. Only reports on fires were uti- 
lized, but other reports were reviewed in 
order to locate any incorrectly filed or 
titled reports. In the review process, 
the fire reports that were considered to 
be minor burn accidents were eliminated. 
For the period 1977-84, MSHA's Health and 
Safety Analysis Center (HSAC) computer 
data base of mine accidents was searched. 
Several fire reports not contained in 
HSAC's files were also provided by MSHA's 
Denver Mining Technology Center, Ventila- 
tion Branch. 

MSHA fire reports were analyzed under 
two headings: underground fires and sur- 
face fires at underground and surface 
mines. 



UNDERGROUND FIRES 

Time Trends 

The first analysis determines time 
trend effects on the number of fires in 
each year. Table 1 lists 229 fire inci- 
dents in underground mines by year of oc- 
currence. The Spearman rank order corre- 
lation, based on table 2, between years 
and number of fires is 0.569, compared 
with the tabled value of 0.432 at the a 
= 0.01 level. This indicates the rank 
order correlation is significant; that 
is, on the average, the number of fires 
reported has increased with time. This 
can be seen in figure 1, which shows 
there were a higher number of fires for 
which a report could be located for the 
period beginning in 1972. 



W W W 



Lfl 



W W i W h 






WWW 



/ / 



www 



y < 



W- 



y / y 



', y 

Rl 1 ^ Wi 



y 
y 

s 

' ft M 






Figure 1. — Underground fire incidents by year, 1950-84. 



The analysis is geared toward a break- 
down by three time periods of mine law: 
pre-1967 Metal and Nonmetal Act, post- 
1967 Metal and Nonmetal Act, and post- 
1977 Mine Health and Safety Act. Table 3 
displays the numbers of fire incidents by 
the three time periods. The chi-square 
for this table is computed on the assump- 
tion of an equal number of fires each 
year. This highly significant value in- 
dicates that differences exist in the 
frequency of occurrence of reported fires 
during the three time periods. This 
could be because prior to 1968 record- 
keeping was not required for accidents 
(including fires) that occurred in metal 
and nonmetal mines. Although the Bureau 
was the designated authority over metal 
and nonmetal mining, investigative re- 
porting of accidents was not undertaken 
on a regular basis, and no specific 
agency was charged with this activity. 
Usually the technical relationship of the 
mine operator with the nearest Bureau 
representative or the seriousness of the 
occurrence were factors determining 
whether or not a fire incident was 
reported. 

Based on discussions with personnel 
from each of the MSHA offices visited 
during this project, it is also apparent 
that a significant percentage of reports 
of fire incidents for this period (pre- 
1968) have been misplaced over the years 
of shift and reorganization of personnel 
and offices in the Bureau, the Mine and 
Environmental Safety Association (MESA), 
and MSHA. If the conservative assumption 
is made that all fire incidents occurring 
after passage of the Metal and Nonmetal 
Mining Act of 1967 have been located, a 

TABLE 3. - Number of reported underground 
fire incidents by three time periods 



Period 


Ob- 
served 


Ex- 
pected 


Average 
per year 


I: 1950-67 

II: 1968-77... 
Ill: 1978-84.. 


61 
92 
76 


118 
65 
46 


3.4 

9.2 

10.9 


Total or av. 


229 


229 


6.5 



level) 



58.32 



(significant at 1-pct 



simple calculation using average fires 
per year shows that possibly 65 pet of 
all fires that occurred before passage of 
the act have not been accounted for. As 
will be shown later in this report, there 
has been a dramatic reduction in the 
average duration of fires reported fol- 
lowing passage of the act and an increase 
in reporting of fire incidents, mandated 
by the creation of MESA and, ultimately, 
MSHA. This supports the hypothesis that 
proportionately more fires less than 24 h 
in length went unreported during the 
early years under consideration. If, on 
the other hand, the assumption of an 
average yearly fire incidence is in 
error, the fire hazardousness of the un- 
derground mining environment must be 
examined. 

Over the years following the mid- 
1960' s, underground metal and nonmetal 
mining equiment has developed an in- 
creased dependency on diesel power and 
electricity as prime movers. This could 
represent a significant source of in- 
crease in fire hazard. Furthermore, the 
growth of the industry during the 1970' s 
in size of operations and number of 
miners employed also represents an over- 
all potential increase in the underground 
fire hazard. 

Significantly then, the trend seen 
in figures 1 and 2 is either toward in- 
creased awareness (via reporting) of 
fires in underground metal and nonmetal 
mines or toward increased hazardousness 
of the environment. 

To fully explain the fire hazard by 
year, the analysis should be based on 
relative measures such as incident rates, 
that is, the number of fires occurring 
per 20 million h worked, the equivalent 
of 10,000 full-time workers per year. 
(See "Data Analysis Methods.") This type 
of analysis was performed for the period 
1978-84, since this was the most current 
period and the only period for which 
the hours could be easily obtained from 
MSHA's data base (table 4). The expected 
number of incidents for each year is com- 
puted on the assumption that the number 
of fires would be in proportion to the 
relative exposure (for example, for 1980 



10 



IB 



16 -- 



tr 




< 

UJ 


14 


y 




IX 




LI 


12 


1 




01 




h 




Z 


10 


LU 




D 




H 




u 


H 


z 




H 




111 




CD 


6 


< 




II 




UJ 




> 




< 


4 



2- 



KEY 



^j Underoround 






1950-67 1968-77 1978-84 

Figure 2. — Average number of fire incidents per year, underground versus surface, during three time periods. 



TABLE 4. - Reported underground fire incidence 
rates, 1978-84 



Year 


Observed 
number of 
incidents 


Hours 

worked, 

10 3 h 


Incidence 
rate 1 


Expected 
number of 
incidents 


1978 


23 

10 

7 

11 

12 

7 

6 


51,900 
55,000 
54,200 
54,500 
37,700 
27,050 
27,400 


8.9 
3.6 
2.6 
4.0 
6.4 
5.2 
4.4 


13 


1979 


14 


1980 


13 


1981 


13 


1982 


9 


1983 


7 


1984 


7 


Total or IR 


76 


307,750 


4.9 


76 



X 2 = 13.05* (significant at 5-pct level). 
! Per 20 million h worked. 



it would be (54,200/307,750) x 76). The 
chi-square value computed from the ob- 
served and expected number of fires indi- 
cates that not all years were equally 



hazardous. This fact can be easily seen 
from figure 3, which also shows that 
there is no apparent time trend on inci- 
dence rates for this period. 



11 



9-- 



7 -■ 



h 6 
< 

H 

ID 5 
U 

z 
111 

Q 

H 4 

u 

z 

H 



3-- 



1-- 



197B 




1982 



KEY 




Underground 



Surface 



11 



1963 19B4 



Figure 3. — Fire incidence rates (based on 20 million h worked), by year, underground versus surface, 1978-84. 



Ore Type 

Table 5 shows underground fires by ore 
type for the three time periods. Analy- 
sis within any given time period indi- 
cates that the differences among differ- 
ent ore types are highly significant; all 
three overall chi-square values are sig- 
nificant at the 0.01 level. The most no- 
ticeable comparison is between ore types 
iron and salt in the period 1950-67. 
These data also show that the distribu- 
tion of fires by ore type has changed 
from period to period. 

According to the t-values, the relative 
frequency of copper fires decreased from 
1968-77 to 1978-84, lead-zinc fires in- 
creased from 1950-67 to 1968-77, iron 
fires decreased from 1950-67 to 1968-77 
and again from 1968-77 to 1978-84, and 
salt fires increased from 1950-67 to 
1968-77. 



Since an estimate of the hours worked 
in each ore type was readily available 
from MSHA's data base for the period 
1978-84, a detailed analysis by ore type 
for this period was performed (table 6). 
The relative measure of rate is based on 
the number of fire incidences per 20 mil- 
lion h worked, which is equivalent to 
10,000 full-time workers per year. (See 
"Data Analysis Methods.") The expected 
number of fires for each type of ore 
mined was computed on the assumption that 
all mines were equally hazardous. Hence, 
the expected number of fires for each ore 
mined would be in proportion to the rela- 
tive exposure (for example, for salt it 
would be (15,400/307,750) * 76). Since 
the chi-square value of 26.55 is highly 
significant, it means all ore types were 
not equally hazardous. The relative mea- 
sure of incidence rates as depicted in 



12 



TABLE 5. - Reported underground fires by principal ore, three time periods 



Ore 



Period I 
1950-67 



No. 



Pet 



Period II 
1968-77 



No. 



Pet 



Period III 
1978-84 



No. 



Pet 



Total 



No. 



Pet 



I vs. 
II 



II vs. 

Ill 



Copper 

Lead-zinc 

Iron 

Salt 

Silver 

Other 

Total specified. 

Specified 

Unspecified 

Total 

X 2 : 

Specified 

Without "Other' 
ND Not determined. 



10 
4 

25 

3 

15 



17.5 
7.0 

43.9 

.0 

5.3 

26.3 



21 

15 
8 

11 
9 

25 



23.6 
16.9 
9.0 
12.4 
10.1 
28.1 



9 
18 

1 
12 

6 
30 



11.8 
23.7 

1.3 
15.8 

7.9 
39.5 



40 
37 
34 
23 
18 
70 



18.0 
16.7 
15.3 
10.4 
8.1 
31.5 



0.87 
1.72' 

4.91* 

2. 76' 
1.04 
ND 



1.95 

1.09 

2.17' 

ND 

ND 

ND 



57 



100.0 



89 



100.0 



76 



100.0 



222 



100.0 



57 

4 



93.4 
6.6 



89 
3 



96.7 
3.3 



76 





100.0 
.0 



222 

7 



96.9 
3.1 



61 



100.0 



92 



100.0 



76 



100.0 



229 



100.0 



45.63 
47.29* 



15.97 
8.81 



41.32 
17. 70 1 



Significant at 5-pct level. 



Significant at 1-pct level. 



TABLE 6. - Average reported underground fire 
incidence rates by ore, 1978-84 



Ore 



Salt 

Lead-zinc 

Silver 

Copper 

Other 2 

Total or IR 



Observed 
number of 
incidents 



12 

18 

6 

9 

31 



76 



Hours 

worked, 

10 3 h 



15,400 
44,050 
15,850 
48.650 
183,800 



307,750 



Incidence 



rate 



15.6 
8.2 
7.6 
3.7 
3.4 



5.0 



Expected 
number of 
incidents 



4 
11 

4 
12 
45 



76 



X = 26.55 (signif icanct at 1 pet level) 
'Per 20 million h worked. 
2 Includes iron (1 incident). 



figure 4 shows salt to be the most haz- 
ardous of all ore types, followed by 
lead-zinc and silver. 

Ignition Source 

Table 7 shows fires by ignition source 
for the three time periods. The overall 
chi-square values indicate that the dif- 
ferent ignition source totals are signif- 
icantly different for each of the three 
time periods. The overwhelming ignition 
source for all the time periods was elec- 
trical. The distribution of specified 
fires among the seven ignition source 
types was very similar for the first two 



time periods but changed for the third 
period. One such category is "Spontane- 
ous combustion," where the proportion of 
fires was significantly down from 15.5 
pet in 1968-77 to 1.4 pet in 1978-84. 
According to the t-test values, the pro- 
portion of electrical fires was also sig- 
nificantly down between 1968-77 and 1978- 
84, but the proportion of engine heat 
fires had increased for the same time 
period. With electrical fires removed, 
the differences among the remaining igni- 
tion sources are significant at the 1-pct 
level for the periods 1968-77 and 1978- 
84, but are not significant for the 1950- 
67 period. 



13 



20 

19-- 

18-- 

17 

16-- 

15-- 

14 -- 

13-- 

12-- 

11- 



UJ 10-- 

u 



9-- 
B-- 

7-- 

6-- 

5- 

4- 

3-- 

2- 

1 -- 







Average (all types)> 





Salt Lead-zinc Silver Copper Other 

Figure 4. — Average underground fire incidence rates (based on 20 million h worked), by ore type, 1978-84. 



Since 1970, there has been some effort 
by persons in the Bureau and MSHA to ban 
smoking in underground metal and nonmetal 
mines. Smoking is, at present, banned in 
certain areas of a mine, such as fueling 
areas. There have been about a half- 
dozen reported underground mine fires di- 
rectly attributed to smoking during the 
study period. These fires involved the 
ignition of mine timbers and lasted 
longer than 24 h, but resulted in no in- 
juries or fatalities. In fires where the 
cause was unspecified, smoking was iden- 
tified as a possible or probable cause in 
at least four cases. 

A survey of MSHA district managers re- 
vealed a cross section of opinions relat- 
ing to the hazardousness of smoking in 
underground metal and nonmetal mines. 



However, most acknowledged that smoking 
materials, where evident of a fire's 
cause, would be the first substance to be 
consumed by the fire and, thus, might be 
involved in more fires than is generally 
known. 

Burning Substance 

Table 8 shows underground fires by 
burning substance for the three time pe- 
riods. One of the underlying assumptions 
in utilizing either the chi-square test 
or the t-test is that of independence. 
This means among other things that any 
given observation falls into and only one 
category. In the case of fires catego- 
rized by burning substances, it would 
mean that each fir* 1 is classified into 



14 



TABLE 7. - Reported underground fires by ignition source, three time periods 



Ignition source 



Period I 
1950-67 


Period II 
1968-77 


Period III 
1978-84 


Total 


1 


t| 


No. 


Pet 


I vs. 
II 


II vs. 


No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 


22 


42.3 


39 


46.4 


21 


29.6 


82 


39.6 


ND 


2.15* 


10 


19.2 


16 


19.0 


7 


9.9 


33 


15.9 


ND 


1.60 


2 


3.8 


7 


8.3 


18 


25.4 


27 


13.0 


1.02 


2.87** 


8 


15.4 


13 


15.5 


1 


1.4 


22 


10.6 


ND 


3.05** 


3 


5.8 


6 


7.1 


9 


12.7 


18 


8.7 


ND 


1.16 


3 


5.8 


1 


1.2 


2 


2.8 


6 


2.9 


ND 


ND 


4 


7.7 


2 


2.4 


13 


18.3 


19 


9.2 


ND 


ND 


52 


100.0 


84 


100.0 


71 


100.0 


207 


100.0 






52 


85.2 


84 


91.3 


71 


93.4 


207 


90.4 




9 


14.8 


8 


8.7 


5 


6.6 


22 


9.6 






61 


100.0 


92 


100.0 


76 


100.0 


229 


100.0 




40.35** 


85.67** 


122.61** 








10. 


40 


23. 


67** 


20 


.10 











Electrical 

Welding sparks or hot 

slag 

Engine heat 

Spontaneous combustion 

Friction 

Explosives 

Other 

Total specified. . . . 

Specified 

Unspecified 

Total 

X 2 : 

Specified 

Without electrical. 



ND Not determined. Significant at 5-pct level. Significant at 1-pct level. 
TABLE 8. - Reported underground fires by burning substance, 1 three time periods 





Per 


iod I 


Period II 
1968-77 


Peri 


od III 


Total 


It| 


Burning substance 


1950-67 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet . 


No. 


Pet 


No. 


Pet 


Ill 




48 
6 
9 
3 

18 


57.1 
7.1 

10.7 
3.6 

21.4 


40 
21 
29 
18 
26 


29.9 
15.7 
21.6 
13.4 
19.4 


19 
31 

16 

9 

12 


21.8 
35.6 
18.4 
10.3 
13.8 


107 
58 
54 
30 
56 


35.1 
19.0 
17.7 
9.8 
18.4 


4.00** 
1.86* 
2.07* 
2.40** 
ND 


1.32 


Combustible liquids... 


3.42** 
ND 




ND 
ND 


Total specified.... 


84 


100.0 


134 


100.0 


87 


100.0 


305 


100.0 






Specified 


84 
3 


96.6 
3.4 


134 
1 


99.3 
.7 


87 
3 


96.7 
3.3 


7 
312 


97.8 
2.2 














87 


100.0 


135 


100.0 


90 


100.0 




100.0 








X 2 : 


¥■ * 

79. QV 


10 
3 


.85* 
.11 


16.*?** 








Without timber. . . . 


14. 


00** 


16. 


82** 





ND Not determined. 
Significant at 5-pct level. 



Significant at 1-pct level. 
In many fires, more than 1 substance was burning. 



only one burning substance type. The 
data on fires by burning substances, of 
course, violates this assumption. How- 
ever, in analyzing the data of this ta- 
ble, it was found that fire in one burn- 
ing substance type was independent of 
fires in other burning substance types. 
If this assumption is true, then the re- 
sults of the analysis given below are 
valid for the intended purpose. The 
large chi-square values for each of the 



three time periods indicate that the dif- 
ferences among the different burning sub- 
stance are significant. These data show 
that timber was the most frequent sub- 
stance burning, while wiring insulation 
and combustible liquids were also fre- 
quently involved in fires, especially 
since 1968. 

The t-test values indicate that the 
distribution of fires by burning sub- 
stance has changed from one period to 



15 



another. There was a significant de- 
crease in the proportion of fires attrib- 
uted to timer from 1950-67 to 1968-77 and 
1978-84. It should be noted, however, 
that the decrease was not significant be- 
tween the second and third time periods. 
The fires due to combustible liquids, on 
the other hand, have increased from one 
period to the next. There was a definite 
shift from timber as the most frequent 
burning substance to combustible liquids, 
insulation, and rubber between 1950-67 
and 1968-77. 

Location 

The locations of fires in underground 
metal and nonmetal mines appear in table 
9. The large chi-square values for the 
three time periods indicate that signif- 
icant differences exist in the frequency 
of fires occurring at various loca- 
tions. Fires occurred predominantly in 
haulageway-drif t entry areas for the pe- 
riods 1968-77 and 1978-84; for the period 
1950-67, they occurred in shaft-raise- 
winze areas. This result also means 
there was a change in the distribution 
of fire location from one period to 
another. The number of fires occurring 
in mined-out wastes and shaft-raise-winze 



areas declined while those in haulageway- 
drift areas increased. To determine the 
sources of fires at the various loca- 
tions, the data on the two most common 
sources were analyzed separately. 

Table 10 shows electrical fires by lo- 
cation for the three time periods. Since 
there are too many categories for the 
number of observations, the expected fre- 
quencies are small (less than five). 
Hence, the chi-square test is not valid 
for this situation. The data in this ta- 
ble and in table 11, therefore, were ana- 
lyzed by the t-test. The t-values for 
all three time periods indicate that the 
relative frequency of electrical fires 
along haulageway-drif t areas, where lit- 
erally miles of cable are installed, was 
more than what would be expected by 
chance. Electrical fires in the moving 
equipment, such as load-haul-dumps, oc- 
curred frequently here. The t-values 
also show the relatively high frequencies 
of electrical fires at substation-shop- 
storage-pump areas for the 1968-77 period 
and at shaft-raise-winze areas for the 
1950-67 period to be significant. In 
comparing the distribution of fires 
across time periods, the t-test revealed 
no significant difference in the pro- 
portion of fires between 1950-67 and 



TABLE 9. - Reported underground fires by location, three time periods 



Location 



Period I 
1950-67 



No. 



Pet 



Period II 
1968-77 



No. 



Pet 



Period III 
1978-84 



No. 



Pet 



Total 



No. 



Pet 



I vs. 

II 



$1 



¥TF 



II VS. 
Ill 



Haulageway-drif t. . . 
Shaft-raise-winze. . 
Mined-out waste. . . , 

Working face , 

Substation-shop- 
storage-pump i 

Other 

Total specified. 

Specified 

Unspecified 

Total 

X 2 : 

Specified 

Without haul- 

ageway-drif t. 

ND Not determined. 



12 

20 

13 

5 

8 
3 



19.7 

32.8 

21.3 

8.2 

13.1 
4.9 



61 



100.0 



61 





100.0 
.0 



61 



100.0 



18.77 



19.06 



42 

11 

10 

9 

16 
3 



46.2 

12.1 

11.0 

9.9 

17.6 
3.3 



42 
9 
2 
6 

6 
6 



59.2 

12.7 

2.8 

8.5 

8.5 
8.5 



96 
40 
25 
20 

30 
12 



43.0 

17.9 

11.2 

9.0 

13.5 
5.4 



3.34 
3.10 1 
1.74* 
ND 

ND 
ND 



1.64 
ND 

1.97 s 
ND 

ND 
ND 



91 



100.0 



71 



100.0 



223 



100.0 



91 

1 



98.9 
1.1 



71 

5 



93.4 
6.6 



223 
6 



97.4 
2.6 



92 



100.0 



76 



100.0 



229 



100.0 



61.11 
6.41 



94.38 
4.28 



Significant at 5-pct level. 



Significant at 1-pct level. 



16 



TABLE 10. - Reported underground electrical fires by location, three time periods 



Location 



Period I 
1950-67 



No. 



Pet 



Period II 
1968-77 



No. 



Pet 



Period III 
1978-84 



No. 



Pet 



Total 



No. 



Pet 



I vs. 
II 



II vs. 
Ill 



Haulageway-drif t. . 
Subs tat ion-shop- 

storage-pump 

Shaft-shaft-winze. 

Working face 

Mined-out waste... 
Other 

Total specified 

Specified 

Unspecified 

Total 



Haulageway-drif t. . 
Subs tat ion-shop- 

storage-pump. 
Shaft-raise-winze. 



31.8 

18.2 

31.8 

9.1 

4.5 
4.5 



13 
3 

4 

1 



46.2 

33.3 

7.7 

10.3 

.0 

2.6 



11 

3 
2 

1 
3 



55.0 

15.0 

10.0 

.0 

5.0 

15.0 



36 

20 

12 

6 

2 

5 



44.4 

24.7 

14.8 

7.4 

2.5 

6.2 



1.09 

1.27 
2.44' 

ND 
ND 
ND 



0.64 

1.50 
ND 
ND 

ND 
ND 



22 



100.0 



39 



100.0 



20 



100.0 



100.0 



22 





100.0 
.0 



39 





100.0 
.0 



20 
1 



95.2 
4.8 



98.8 
1.2 



22 



100.0 



39 



100.0 



21 



100.0 



82 



100.0 



1.91' 

0.19 
1.91' 



4.94 

2.79* 

ND 



4.60 

ND 
ND 



ND Not determined. 



Significant at 5-pct level. 



Significant at 1-pct level. 



TABLE 11. - Reported underground welding or cutting fires 
by location, three time periods 



Location 



Shaft-raise-winze. 
Haulageway-drif t. . 
Substation-shop- 
storage-pump. 
Mined-out waste. . . 

Working face , 

Other , 

Total , 



1950-67 



No. 



10 



Pet 



60.0 
20.0 

20.0 
.0 
.0 
.0 



100.0 



1968-77 



No. 



16 



Pet 



37.5 
43.8 

.0 

6.3 

.0 

12.5 



100.0 



1978-84 



No. 



Pet 



42.9 
28.6 

28.6 
.0 
.0 
.0 



100.0 



Total 



No. 



15 
11 

4 
1 

2 



33 



Pet 



45.5 
33.3 

12.1 

3.0 

.0 

6.1 



100.0 



Shaft-raise-winze. 
Haulageway-drif t. . 



4.44 
2.57 1 



Significant at 1-pct level. 

1968-77, and between 1968-77 and 1978-84 
for the haulageway-drif t entry areas and 
substation-shop-storage-pump areas. The 
same analysis for the shaft-raise-winze 
area, on the other hand, showed a signif- 
icant decline in the proportion of fires 
from 1950-67 to 1968-77. 

Table 11 contains the analysis for 
welding-cutting fires by location for two 
of the time periods. Owing to the small 



sample size in each period, which leads 
to large fluctuations, the total number 
of fires was analyzed so that statisti- 
cally meaningful conclusions could be 
drawn from these data. The t-tests for a 
one-sample case showed that fires from 
welding or cutting operations occurred 
more frequently in the mine shaft-raise- 
winze and in haulageway-drif t areas than 
in other areas of the mine. 



17 



Equipment Involved 

Table 12 categorizes fires by equipment 
involved, for the three time periods. 
During the tabulation of these data, it 
became obvious that some changes in the 
reporting mechanism have occurred over 
time for the "Unspecified," "None," and 
"Unknown" categories. The data for these 
categories, therefore, are such that it 
is not possible to obtain a separate fire 
count for each category. It should be 
noted that the combination of the three 
categories comprises a major portion of 
all the fires by equipment type. Where 
equipment is specified, the chi-square 
values for the last two time periods are 
significant, which indicates that some 
equipment types were more involved in 
fires than others. The most prone pieces 
of equipment were either mobile, such as 
load-haul-dumps, or electrical (that is, 
stationary electrical equipment) . Two 
t-tests were performed for the mobile and 
electrical equipment. The first compared 
the 1950-67 and 1968-77 periods; the sec- 
ond compared the 1968-77 and 1978-84 
periods. All of the t-values were not 
significant. 

To fully explain the relative fire haz- 
ard of the various types of equipment 
used in underground mines, fire incidents 



should be normalized based on actual ex- 
posure hours or the number of equipment 
pieces. Although some data to support 
such an analysis were located, it was 
found that the data available were inade- 
quate to normalize the equipment most 
frequently associated with underground 
fires. The authors believe that esti- 
mates of equipment populations beyond the 
scope of presently available data would 
lead to highly questionable results; 
therefore, no attempt was made to compute 
incidence rates by equipment for under- 
ground fires at this time. 

An analysis of the leading ignition 
source of fires where equipment is in- 
volved is presented in table 13. As in 
table 12, the equipment category "Unspe- 
cified-unknown -none" comprises a major 
portion of all the electrical fires. 
Also, as explained before, the small num- 
ber of fires precludes the use of the 
chi-square test for this table. The 
t-tests show that the relative frequency 
of electrical equipment in electrical ig- 
nition fires was much higher than the 
expected (0.25) for all time periods. 
The same type of analysis also shows that 
the relative frequency of mobile equip- 
ment was significantly more than expected 
for the period 1968-77. 



TABLE 12. - Reported underground fires by equipment involved, three time periods 





Per 


iod I 


Period II 


Period III 


Total 


It| 


Equipment 


1950-67 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 




6 

10 
1 
6 


26.1 

43.5 

4.3 

26.1 


24 

16 

5 

7 


46.2 

30.8 

9.6 

13.5 


31 
9 
6 
6 


59.6 
17.3 
11.5 
11.5 


61 
35 
12 
19 


48.0 

27.6 

9.4 

15.0 


1.64 

1.07 

ND 

ND 


1.38 




1.61 

ND 


Other 


ND 






Total specified.... 


23 


100.0 


52 


100.0 


52 


100.0 


127 


100.0 








23 
38 


37.7 
62.3 


52 
40 


56.5 
43.5 


52 
24 


68.4 
31.6 


127 
102 


55.5 
45.5 




Unspecif ied-unknown- 










61 


100.0 


92 


100.0 


76 


100.0 


229 


100.0 










7.09 


17.69** 


33.69** 









ND Not determined. 
# * 

Significant at 1-pct level. 

1 The reporting mechanism did not permit the classification of fires into 3 separate 

categories. 



18 



TABLE 13. - Reported underground electrical fires by equipment, three time periods 



El 



Equipment 



Period I 
1950-67 



No. 



Pet 



Period II 
1968-77 



No. 



Pet 



Period III 
1978-84 



No. 



Pet 



Total 



No. 



Pet 



I vs. 
II 



II vs. 
Ill 



Electrical 

Mobile , 

Conveyor 

Other 

Total specified.. 

Specified 

Unspecif ied-unknown- 
none 

Total 



54.5 

36.4 

.0 

9.1 



12 

15 

I 



42.9 

53.6 

.0 

3.6 



47.1 

41.2 

5.9 

5.9 



26 
26 

1 
3 



46.4 

46.4 

1.8 

5.4 



0.66 

.97 

ND 

ND 



ND 
ND 
ND 
ND 



11 



100.0 



28 



100.0 



17 



100.0 



56 



100.0 



11 



11 



50.0 



50.0 



28 



11 



71.8 



28.2 



17 



81.0 



19.0 



56 



26 



68.3 



31.7 



22 



100.0 



39 



100.0 



21 



100.0 



82 



100.0 



t| 



Electrical. 
Mobile 



2.26 
.87 



2.19 
3.49 J 



2.10 

1.54 



ND Not determined. Significant at 5-pct level. Significant at 1-pct level. 
TABLE 14. - Reported underground fires by means of detection, three time periods 





Period I 


Period II 
1968-77 


Period III 


Total 


It| 


Means of detection 


1950-67 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pct 


No. 


Pet 


Ill 


Operator-worker 


9 

20 
3 
8 
7 
7 


16.7 

37.0 
5.6 
14.8 
13.0 
13.0 


28 

23 

10 

6 

8 

14 


31.5 

25.8 

11.2 

6.7 

9.0 

15.7 


29 

21 
7 
6 

3 


43.9 

31.8 
10.6 

9.1 
.0 

4.5 


66 

64 
20 
20 
15 
24 


31.6 

30.6 
9.6 
9.6 
7.2 

11.5 


1.96* 

1.42 
1.15 

1.57 

ND 
ND 


1.59 


Workers (not 


.82 


Shift boss-foreman.... 


ND 
ND 
ND 




ND 






Total specified. . . . 


54 


100.0 


89 


100.0 


66 


100.0 


209 


100.0 






54 
7 


88.5 
11.5 


89 
3 


96.7 
3.3 


66 
10 


86.8 
13.2 


209 
20 


91.3 
8.7 














61 


100.0 


92 


100. 0_, 


76 


100.0 


229 


100.0 










18.44** 


26. 


21** 


59.09** 






ND Not determined. 

Means of Det 


Signi 
ectio 


f icant 
n 


at 5- 


pet lev 
The 


el. 

t-te 


**Sign 
st show 


ifica 
s the 


nt at 1 
re was 


-pet level, 
a significant 



The person(s) discovering a fire are 
listed in table 14. The large chi-square 
values for each of the three time periods 
indicate that the frequencies for the six 
different categories are statistically 
different. The most frequent detection 
of fire occurs Immediately or after a 
short period of time by workers In the 
area. Most metal and nonmetal mine fire 
reports do not identify the specific job 
title of the person discovering a fire. 



increase in the relative frequency of the 
category "Operator-worker (immediate)" 
between the periods 1950-67 and 1968-77. 
The same type of analysis, however, shows 
the changes to be nonsignificant for the 
next three categories. 

Duration 

Duration of fires appears in table 15. 
Note that for the periods 1950-67 and 
1978-84, the duration is not specified 



19 



TABLE 15. - Reported underground fires by duration, three time periods 





I 
1950-67 


II 
1968-77 


III 


Total 


|t| 


Duration, h 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 




5 
2 
4 
8 
23 


11.9 
4.8 
9.5 

19.0 
54.8 


11 
5 
31 
20 
17 


13.1 

6.0 

36.9 

23.8 

20.2 


8 
6 

21 
8 

14 


14.0 
10.5 
36.8 
14.0 
24.6 


24 
13 
56 
36 
54 


13.1 

7.1 

30.6 

19.7 

29.5 


ND 

ND 
3.23** 

ND 
3.92** 


ND 




ND 




ND 




1.43 


24+ 


ND 






Total specified.... 


42 


100.0 


84 


100.0 


57 


100.0 


183 


100.0 








42 
19 


68.9 
31.1 


84 
8 


91.3 
8.7 


57 
19 


75.0 
25.0 


183 
46 


79.9 
20.1 










61 


100.0 


92 


100.0 


76 


100.0 


229 


100.0 






33. 


95** 


22. 


90** 


13.26* 







Significant at 5-pct level. 



Significant at 1-pct level. 



for an estimated 30 and 25 pet, respec- 
tively, of all the reported fires. It 
should also be noted that many of the 
fires lasting less than 1/2 h were not 
reportable based on duration. Most of 
these were reportable because of an asso- 
ciated injury; some were reported as a 
courtesy; and others were investigated by 
MSHA inspectors after hearing about the 
fire from a third party. As a general 
rule, reports of these fires were found 
at MSHA subdistrict offices in the form 
of internal memos or letter reports. 

Of those fires that were reported and 
where the duration is specified, the chi- 
square values are significant for all the 
periods. This means the number of fires 
are not evenly distributed across the 
five duration categories. In the 1950-67 
time period, the most frequent duration 
was 24 h or more. The t-test value be- 
tween the 1950-67 and 1968-77 periods in- 
dicates there was definitely a decline in 
the relative frequency of fires for this 
category. Based on these results and on 
discussions with the concerned officials, 
it can be concluded that prior to 1968 
fires lasting 24 h or longer were more 
frequently reported than others. 

Further analysis of ignition sources by 
duration was performed for two time peri- 
ods, 1968-77 and 1978-84, and the results 
are presented in table 16. It should be 
noted that for period 1978-84, the data 
on duration of fires are less than com- 
plete. In about 25 pet of the reports, 



the duration of the fire was unspecified. 
Of the specified durations in both time 
periods, all the spontaneous combustion 
fires lasted 24 h or longer, and about 50 
pet of the electrical ignition fires 
lasted 1 to 4 h. 

Number of Injuries 

Fire injuries for the three time peri- 
ods appear in table 17. In all the time 
periods, the fires where no injuries oc- 
curred comprise an overwhelming propor- 
tion of all the fires. Once the fires 
with no injuries are eliminated, the sam- 
ple size for each of the time periods 
becomes too small to draw any statisti- 
cally meaningful conclusions. A cross- 
tabulation of injury fires by ignition 
source appears in table 18. As shown, 
the source of most injury fires was elec- 
trical, followed by welding and engine 
heat. Prior to 1978, there were no in- 
juries involved with fires occurring from 
engine heat. Yet, during the 1978-84 
time period, engine heat was the largest 
source of all injury fires. Cross-tabu- 
lations of injury fires by location and 
equipment appear in tables 19 and 20. 
Injury fires occurred predominantly along 
haulageway-drif ts, followed by working 
face areas. Prior to 1968, it appears 
that more injury fires started at the 
shaft or in a mined-out area. Since 
1968, they seem to have occurred more in 
haulageway-drif ts and working face areas. 



20 



TABLE 16. - Reported underground fires by ignition source and duration, 
two time periods 



Ignition source 



to 0.5 h 



1968-77 



1978-84 



0.5 to 1.0 h 



1968-77 



1978-84 



1+ to 4 h 



1968-77 



1978-84 



4+ to 24 h 



1968-77 



1978-84 



Electrical , 

Welding sparks or 

hot slag 

Engine heat 

Spontaneous 

combustion 

Friction 

Explosives 

Other 

Unspecified 

Total 

Electrical 

Welding sparks or 

hot slag 

Engine heat 

Spontaneous 

combustion 

Friction 

Explosives 

Other 

Unspecified 

Total 



19 

3 
2 


3 

2 
2 



11 


3 


3 

3 

1 



11 



31 



21 



20 



24+ h 



1968-77 



1 

2 
1 

12 
1 







17 



Unspecified 



Total 



1978-84 



1968-77 



14 



8 



1978-84 



1968-77 



39 

16 
7 

13 
6 
1 
2 



19 



92 



1978-84 



21 



1 
9 
2 
13 
5 



76 



TABLE 17. - Reported underground fires by number of injuries, 
three time periods 



Number of injuries 


1950-67 


1968-77 


1978-84 


Total 




No. 


Pet 


No. 


Pet 


No. 


Pet 


No. 


Pet 





54 
4 
2 
1 



88.5 

6.6 

3.3 

1.6 

.0 


85 
3 
3 
1 



92.4 

3.3 

3.3 

1.1 

.0 


63 

11 

2 






82.9 

14.5 

2.6 

.0 

.0 


202 

18 

7 

2 




88.2 


1 


7.9 


2 to 5 

10 + 


3.1 
.9 
.0 








61 


100.0 


92 


100.0 


76 


100.0 


229 


100.0 







TABLE 18. - Reported underground injury fires 
by ignition source, three time periods 



Ignition source 

Electrical 

Welding sparks or hot slag 

Engine heat 

Spontaneous combustion. . . . 

Friction 

Other 

Total 



1950-67 



1968-77 



1978-84 



Total 



13 



27 



21 



The type of equipment most involved in 
injury fires was mobile-type equipment. 
In fact, in the 1978-84 period, all of 
the injury fires with a known equipment 
type involved mobile equipment. 

Number of Deaths 

Table 21 lists fires by number of 
deaths. The only significant result is 
the overall reporting frequency of non- 
fatal fires. Once the nonfatal fires are 
removed, the sample sizes in each of the 
three periods become too small to draw 
any statistically meaningful conclusions. 

Mining Method 

Table 22 shows fires by mining method 
for the three time periods. For a large 



portion of the fire reports, mining meth- 
od was not specified for the 1950-67 and 
1978-84 periods. The chi-square values 
for all time periods indicate significant 
differences among the fire frequencies 
associated with the five specified mining 
methods. The t-test values show the fire 
incidences occurred with a higher than 
expected relative frequency in the caving 
method for the period 1950-67 and in the 
room-and-pillar method for the periods 
1968-77 and 1978-84. The t-values show 
that the relative frequency of fires in- 
creased from one period to the next for 
the room-and-pillar method and decreased 
for the caving method. These results in- 
dicate that the distribution of the fire 
incidents for the mining methods has 
changed from period to period. For the 
open stoping method, however, the change 



TABLE 19. - Reported underground injury fires by location, 
three time periods 



Location 

Haulageway-drif t 

Working face 

Shaft-raise-winze 

Substation-shop-storage-pump 

Mined-out area 

Other 

Unspecified 

Total 



1950-67 



1968-77 



1978-84 



Total 



10 
6 
3 
3 
2 
2 
1 



13 



27 



TABLE 20. - Reported underground injury fires by equipment, 
three time periods 



Equipment 

Mobile 

Electrical 

Other 

Unspecified-unknown -none. 
Total 



1950-67 



1968-77 



1978-84 



Total 



11 


2 



13 



14 
3 
1 
9 



27 



TABLE 21. - Reported underground fires by number of deaths, 
three time periods 



Number of deaths 


1950-67 


1968-77 


1978-84 


Total 




No. 


Pet 


No. 


Pet 


No. 


Pet 


No. 


Pet 





57 
2 

2 


93.4 

3.3 

.0 

3.3 


86 
2 
2 
2 


93.5 
2.2 
2.2 
2.2 


76 





100.0 
.0 
.0 
.0 


219 
4 
2 

4 


95.6 


1 


1.7 


6+ 


.9 
1.7 








61 


100.0 


92 


100.0 


76 


100.0 


229 


100.0 







22 



TABLE 22. - Reported underground fires by mining method, three time periods 



M 



Mining method 



Period I 
1950-67 



No, 



Pet 



Period II 
1968-77 



No. 



Pet 



Period III 
1978-84 



No. 



Pet 



Total 



No. Pet 



I vs. 
II 



II vs. 

Ill 



Roora-and-pillar. . . 

Caving 

Open stoping 

Cut-and-fill 

Other 

Total specified 

Specified 

Unspecified 

Total 

X 2 : Specified.... 

|t|: 

Room and pillar 
Caving 

ND Not determined 



10 

21 

13 

1 

6 



19.6 
41.2 
25.5 
2.0 
11.8 



31 
18 

16 

14 

7 



36.0 
20.9 
18.6 
16.3 
8.1 



34 
5 
5 

10 
5 



57.6 
8.5 
8.5 

16.9 
8.5 



75 
44 
34 
25 
18 



38.3 
22.4 
17.3 
12.8 
9.2 



2.03 
2.54' 
1.02 
2.59 1 
ND 



2.57' 
2.02* 
1.70* 
ND 
ND 



51 



100.0 



86 



100.0 



59 



100.0 



196 



100.0 



51 
10 



83.6 
16.4 



86 
6 



93.5 
6.5 



59 
17 



77.6 
22.4 



196 
33 



85.6 
14.4 



61 



100.0 



92 



100.0 



76 



100.0 



229 



100.0 



22.23 

ND 
3.78* 



17.84 



3.72 



53.80 



7.23 



ND 



ND 



* 3Flf 

Significant at 5-pct level. Significant at 1-pct level. 



TABLE 23. - Reported underground fires by successful extinguishing 
agent, 1 three time periods 



Extinguishing agent 


1950-67 


1968-77 


1978-84 


Total 




No. 


Pet 


No. 


Pet 


No. 


Pet 


No. 


Pet 




26 

5 

9 

18 

10 


38.2 
7.4 
13.2 
26.5 
14.7 


43 
27 
18 
10 
24 


35.2 
22.1 
14.8 
8.2 
19.7 


20 

16 

7 

3 

5 


39.2 

31.4 

13.7 

5.9 

9.8 


89 
48 
34 
31 
39 


36.9 




19.9 




14.1 




12.9 
16.2 






Total specified.... 


68 


100.0 


122 


100.0 


51 


100.0 


241 


100.0 




68 
3 


95.8 
4.2 


122 
3 


97.6 
2.4 


51 
34 


60.0 
40.0 


241 
40 


85.8 




14.2 


Total 1 


71 
61 


100.0 
NAp 


125 
92 


100.0 
NAp 


85 
76 


100.0 

NAp 


281 
229 


100.0 




NAp 



NAp Not applicable. 
More than one successful extinguishing agent was used in some fires. 



is significant only from 1968-77 to 1978- 
84. The relative frequency of the cut- 
and-fill also increased from 1950-67 to 
1968-77. 

To better explain the relative fire 
hazard of the various types of mining 
methods, it would be more appropriate to 
relate the fires to the average number of 
mines associated with each mining method 
and time period. As no reliable data on 
the average number of mines by mining 
methods were available, this type of 
analysis was not performed. 



Successful Extinguishing Agent 

Tables 23 and 24 delineate fires by 
successful extinguishing agent for the 
three time periods. Table 23 gives the 
frequency with which an extinguishing 
agent was successfully used. The fires 
in which two agents were successfully 
used were entered under both categories 
in this table. Table 24 gives the bivar- 
iate distribution of the fires, showing 
which extinguishing agents were used 
together. Note that in 1978-84, the 



23 



TABLE 24. - Reported underground fires, joint distribution of successful 
extinguishing agents, by three time periods 



Period 1 

Water 

Dry chemical. . . 

Burned out 

Sealing 

Other 

Unspecified. . . . 
l I: 1955-67; II 



Water 



II 



III 



Dry chemical 



II 



III 



Burned out 



II 



III 



Sealing 



II 



III 



Other 



II 



III 



Unspecified 



II III 



19 



14 



13 



3 

10 



2 

4 

10 



34 



1968-77; III: 1978-84. 

TABLE 25. - Reported surface fire incidents by year 





Number of 




Number of 




Number of 


Year 


incidents 


Year 


incidents 


Year 


incidents 


1950... 


1 


1962... 


4 


1974... 


10 


1951... 





1963... 


3 


1975... 


5 


1952... 





1964... 


2 


1976... 


12 


1953... 


1 


1965... 





1977... 


13 


1954... 





1966... 





1978... 


29 


1955... 





1967... 


1 


1979... 


31 


1956... 


3 


1968... 


4 


1980... 


16 


1957... 


1 


1969... 


4 


1981... 


21 


1958... 


1 


1970 


4 


1982 1 .. 


5 


1959... 


1 


1971 


2 


1983... 


10 


1960... 



3 


1972... 
1973 


6 
5 


1984... 
Total 


14 


1961... 


212 



Statistics for 1982 in surface mining of stone, clay, col- 
loidal phosphate, and sand and gravel are based on July through 
December only. These operations were excluded from MSHA juris- 
diction by House Joint Resolution 370, December 15, 1981. On 
July 15, 1982, the Congress approved House Resolution 6685, 
which restored MSHA's jurisdiction to all operations except 
those of States or political subdivisions. 



successful extinguishing agent was not 
specified in about 45 pet (34/76) of the 
fire reports. Where the extinguishing 
agents were specified, it was found that 
none of the standard statistical tests 
were applicable, as the basic assumption 
of independence was violated. That is, 
water and dry chemicals were used more 
frequently than other agents in fires in- 
volving two agents. Hence, the following 
conclusions are based on simple examina- 
tion of the data: (1) in 1968-77, the 
frequency with which two successful ex- 
tinguishing agents were used is much 
higher than in the other two periods, 
(2) water was the predominant agent in 



all three periods, (3) there was a defi- 
nite shift from sealing to dry chemical, 
and (4) the relative frequency of "Burned 
out" was approximately the same through- 
out the three periods. 

SURFACE FIRES AT SURFACE 
AND UNDERGROUND MINES 

Time Trends 

As with underground fires, the first 
analysis looked at the time trends. Ta- 
ble 25 lists 212 fire incidents by year 
for surface fires. The number of fires 
for 1982 is based only on July through 



24 



December for stone, clay, colloidal 
phosphate, and sand and gravel, because 
these operations were excluded from 
MSHA's jurisdiction from January through 
June of that year. 

It can be seen from table 25 and fig- 
ure 5 that there were a higher number of 
fires for which a report could be located 
for the period beginning in 1972. This 
fact is further confirmed by the Spearman 
rank order correlation test based on ta- 
ble 26. The highly significant r s value 
of 0.855 indicates that, on the average, 
the number of fires reported increased 
with time. 

Table 27 displays the number of fire 
incidents by three time periods. The 
chi-square for this table is computed on 
the assumption of an equal number of 
fires for each year. This highly signif- 
icant value indicates, as shown in figure 



2, that differences exist in the fre- 
quency with which surface fires were re- 
ported during the three time periods. As 
with underground fires, this could be be- 
cause prior to 1968 there was no record- 
keeping requirement for accidents (in- 
cluding fires) that occurred in metal and 
nonmetal mines. Also, a significant per- 
centage of reports of fire incidents dur- 
ing this period (pre-1968) have been 
misplaced over the years of shift and re- 
organization of personnel and offices in 
the Bureau and MSHA. 

Significantly then, the trend as seen 
in figures 2 and 5 is either toward in- 
creased awareness (via reporting) of 
fires in surface metal and nonmetal mines 
or toward an increasingly hazardous envi- 
ronment, or both. 

Table 28 gives the surface incidence 
rates for the period 1978-84. These 



n , , n 



$$$ 



W-H 



$_ 



UM 



IV 



14 



1 1> 



/ s / 

W WW 



/ 

/ 
/ 
/ 

', 

111 

in 



n\ 



*** 






www 



1 1 



J4LJ4 



Figure 5. — Surface fire incidents by year, 1950-84. 



25 



TABLE 26. - Ranking of reported surface fire incidents by year 



Year 



Number of 
incidents 



Rank 



Year Incidents 



Year 



Number of 
incidents 



Rank 



Year Incidents 



1950. 
1951. 
1952. 
1953. 
1954. 
1955. 
1956. 
1957. 
1958. 
1959. 
1960. 
1961. 
1962. 
1963. 
1964. 
1965. 
1966. 
1967. 



1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 



10.5 

4.0 

4.0 

10.5 

4.0 

4.0 

17.0 

10.5 

10.5 

10.5 

4.0 

17.0 

20.5 

17.0 

14.5 

4.0 

4.0 

10.5 



1968 

1969 

1970 

1971 

1972 

1973.... 

1974 

1975 

1976 

1977 

1978 

1979 

1980 

1981 

1982 1 . ... 

1983 

1984 

Total. 



4 

4 

4 

2 

6 

5 

10 

5 

12 

13 

29 

31 

16 

21 

5 

10 

14 



19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 



20.5 
20.5 
20.5 
14.5 
26.0 
24.0 
27.5 
24.0 
29.0 
30.0 
34.0 
35.0 
32.0 
33.0 
24.0 
27.5 
31.0 



212 



NAp 



NAp 



5FTT 

= 0.855 (significant at 1-pct level), 
surface mining of stone, clay, colloidal phosphate, and 
on July through December only. These operations were ex- 
ion by House Joint Resolution 370, December 15, 1981. On 
ss approved House Resolution 6685, which restored MSHA's 
ions except those of States or political subdivisions. 



NAp Not applicable. r 
Statistics for 1982 in 
sand and gravel are based 
eluded from MSHA jurisdict 
July 15, 1982, the Congre 
jurisdiction to all operat 



TABLE 27. - Number of surface fire incidents by three time periods 



Period 



Ob- 
served 



Ex- 
pected 



Average 
per year 



Period 



Ob- 
served 



Ex- 
pected 



Average 
per year 



I: 
II: 



1950-67 

1968-77... 



21 
65 



109 
61 



1.2 
6.5 



III: 1978-84. 
Total or av. 



126 



42 



18.0 



212 



212 



6.1 



239.31 (significant at 1-pct level). 



TABLE 28. 
1978-84 



Reported surface fire incidence rates, 



Year 


Observed 
number of 
incidents 


Hours 

worked, 

10 3 h 


Incidence 
rate 1 


Expected 
number of 
incidents 


1978 


29 
31 
16 
21 
5 
10 
14 


418,650 
440,200 
417,100 
400,350 
221,550 
289,150 
299,450 


1.4 
1.4 
.8 
1.0 
.4 
.7 
.9 


21 


1979 


22 


1980 


21 


1981 


20 


1982 


H 


1983 


15 


1984 


15 






Total or IR 


126 


2,486,450 


1.0 


126 



X 2 = 13.16 (significant at 5-pct level) 
1 Per 20 million h worked. 



26 



incidence rates are equivalent to the 
number of fires per 10,000 full-time 
workers (See "Data Analysis Methods.") 
The chi-square values computed from the 
observed and expected number of fires in- 
dicate that not all years were equally 
hazardous. Figure 3 shows years 1978 and 
1979 to have the highest incidence rate. 

Ore Type 

Table 29 shows surface fires by ore 
type for the three time periods. Fires 
occurred most often at surface limestone 
and iron mines , especially for the period 
1978-84. The chi-square test for the pe- 
riod 1968-77 indicates that the differ- 
ences in ore totals, after the "Other" 
category is eliminated are not signifi- 
cant. This test was not performed for 



the period 1950-67 because 11 fires among 
4 different categories yield an expected 
frequency of less than 3 fires per cate- 
gory. An examination of the data for 
this period shows that the frequency 
of fires was the highest in iron ore. 
According to the t-values, the only sig- 
nificant change in the relative fre- 
quency was in iron ore between 1950-67 
and 1968-77. 

A detailed analysis by ore type was 
also performed for the most current peri- 
od, 1978-84 (table 30). The chi-square 
value of 12.71 is significant at the 
5-pct level, indicating that all ore 
types were not equally hazardous. The 
relative measure of incidence rates as 
depicted in figure 6 shows iron to be the 
most hazardous and sand and gravel to be 
the least hazardous. 



TABLE 29. - Reported surface fires by principal ore, three time periods 





Period I 
1950-67 


Peri 


od II 


Period III 


Total 


It| 


Ore 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 




1 
7 
3 



7 


5.6 

38.9 

16.7 

.0 

38.9 


9 
5 
5 
5 
31 


16.4 
9.1 
9.1 
9.1 

56.4 


24 

18 

9 

9 

64 


19.4 

14.5 

7.3 

7.3 

51.6 


34 

30 

17 

14 

102 


17.3 

15.2 

8.6 

7.1 

51.8 


1.16 
2.96** 

.89 

1.33 

ND 


0.48 
1.00 




.42 




.42 
ND 


Total specified. . . . 


18 


100.0 


55 


100.0 


124 


100.0 


197 


100.0 








18 
3 


85.7 
14.3 


55 

10 


84.6 
15.4 


124 
2 


98.4 
1.6 


197 
15 


92.9 
7.1 














21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 








X 2 : Specified without 


ND 


2.00 


10.80* 









ND Not determined. 



Significant at 5-pct level. 



Significant at 1-pct level. 



TABLE 30. - Average reported surface fire incidence rates 
by ore, 1978-84 



Ore 


Observed 
number of 
incidents 


Hours 

worked, 

10 3 h 


Incidence 
rate 1 


Expected 
number of 
incidents 




18 

24 

9 

9 

66 


198,350 
458,400 
236,850 
362,400 
1,230,450 


1.8 

1.0 

.8 

.5 

1.1 


10 


Crushed limestone 
Sand and gravel. . 


23 
12 
19 
62 






Total or IR 


26 


2,486,450 


1.0 


126 



,2 _ 



= 12.71 (significant at 5-pct level). . 
: Per 20 million h worked. 
2 Includes 2 incidents in unspecified ores. 



27 



1.B-- 



1.6-- 



< 

DC 



111 i 

U 

z 
111 

Q 

H -B + 

u 

Z 

H 

.6- 



.4-- 



Average (all types)- 





Iron Crushed limestone Copper Sand and gravel Other 

Figure 6. — Average surface fire incidence rates (based on 20 million h worked), by ore type, 1978-84. 



Ignition Source 

Table 31 shows fires by ignition source 
for the three time periods. The number 
of unspecified fires comprises a major 
portion of the total fires, especially 
for the 1978-84 period, thus raising some 
questions on the completeness of the 
data. The chi-square values with and 
without the "Other" category indicate 
that the different ignition source to- 
tals are significantly different for the 
time periods 1968-77 and 1978-84. No 
chi-square test was performed for the 
first period as there were too few obser- 
vations. It is apparent, however, that 
the leading ignition source for this pe- 
riod was electrical. The t-tests also 
show that the proportion of engine heat 



fires increased from 1968-77 to 1978-84 
while the proportion of electrical fires 
declined over the same time. 

Burning Substance 

The data on surface fires by burning 
substance for the three time periods are 
shown in table 32. In analyzing the data 
of this table, the same basic assumption 
was made on independence of burning sub- 
stances as outlined for its counterpart 
table 8 on underground fires. The chi- 
square test shows that the differences in 
the frequency with which the various sub- 
stances were involved in fires were sig- 
nificant for the periods 1968-77 and 
1978-84 but not for the period 1950-67. 
The relative frequency of combustible 



28 



TABLE 31. - Reported surface fires by ignition source, three time periods 





Period I 
1950-67 


Peri 


od II 


Period III 


Total 


It| 


Ignition source 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 




1 
6 
3 
1 
8 


5.3 
31.6 
15.8 

5.3 

42.1 


9 
15 
11 

1 
20 


16.1 

26.8 

19.6 

1.8 

35.7 


38 
16 
22 
8 
18 


37.3 
15.7 
21.6 

7.8 
17.6 


48 
37 
36 
10 
46 


27.1 
20.9 
20.3 
5.6 
26.0 


1.20 

.40 

.37 

ND 

ND 


2.79** 




1.68* 




ND 




ND 




ND 






Total specified. . . . 


19 


100.0 


56 


100.0 


102 


100.0 


177 


100.0 








19 

2 


90.5 
9.5 


56 
9 


86.2 
13.8 


102 
24 


81.0 
19.0 


177 
35 


83.5 
16.5 














21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 




X 2 : 


ND 

ND 


17. QT** 


24.fiR** 








11. 


56** 


23. 


05** 





ND Not determined. Significant at 5-pct level. Significant at 1-pct level. 
TABLE 32. - Reported surface fires by burning substance, 1 three time periods 





Period I 
1950-67 


Period II 


Period III 


Total 


It| 


Burning substance 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 


Combustible liquids... 
Construction material. 


4 
5 
5 
4 
11 
7 


11.1 
13.9 
13.9 
11.1 
30.6 
19.4 


24 
19 
11 
9 
6 
16 


28.2 
22.4 
12.9 
10.6 
7.1 
18.8 


70 

25 

8 

11 

3 

9 


55.6 
19.8 
6.3 
8.7 
2.4 
7.1 


98 
49 
24 
24 
20 
32 


39.7 

19.8 

9.7 

9.7 

8.1 

13.0 


2.04* 
1.07 

ND 

ND 
3.40** 

ND 


3.92** 

ND 
1.64 




ND 




1.65* 




ND 






Total specified.... 


36 


100.0 


85 


100.0 


126 


100.0 


247 


100.0 








36 



100.0 
.0 


85 
1 


98.8 
1.2 


126 
9 


93.3 
6.7 


247 
10 


96.1 
3.9 














36 


100.0 


86 


100.0 


135 


100.0 


257 


100.0 








X 2 : 


6. 


00NS 
ND 


16. 1 * l 


150-1Q** 








Without combus- 
tible liquids. . . . 


h 


ID 


24 


.36* 





ND Not determined. 

Significant at 5-pct level. **Signif icant at 1-pct level. 
1 In many fires, more than 1 substance was burning. 



liquids fires definitely increased across 
time periods, while that of timber 
decreased. 

Location 

The locations of fires in surface metal 
and nonmetal mines appear in table 33. 
For the first two time periods, the over- 
whelming majority of fires occurred in 



the surface building location, while for 
the last period, the split was about SO- 
SO between the surface building and a 
surface location other than the building. 

Equipment Involved 

Table 34 shows surface fires by equip- 
ment for the three time periods. As with 
its counterpart table 12 on underground 



29 



TABLE 33. - Reported surface fires by location, three time periods 



E 



Location 



Period I 
1950-67 



No. 



Pet 



Period II 
1968-77 



No. 



Pet 



Period III 
1978-84 



No. 



Pet 



Total 



No. 



Pet 



I vs. 

II 



II vs. 

Ill 



Surface building. . 

Surface 

Other 

Total specified 

Specified 

Unspecified 

Total 

ND Not determined 



16 


4 



80.0 

.0 

20.0 



44 



21 



67.7 

.0 

32.3 



54 

67 





44.6 

55.4 

.0 



114 
67 
25 



53.3 
32.5 
12.1 



1.06 
ND 

ND 



3.00 
7.50* 
ND 



20 



100.0 



65 



100.0 



121 



100.0 



206 



100.0 



20 
1 



95.2 
4.8 



65 




100.0 
.0 



121 
5 



96.0 
4.0 



206 
6 



97.2 
2.8 



21 



100.0 



65 



100.0 



126 



100.0 



212 



100.0 



Significant at 1-pct level. 



TABLE 34. 



Reported surface fires by equipment involved, three time periods 





Period I 
1950-67 


Period II 


Period III 


Total 


It| 


Equipment 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 






1 

2 

14 


0.0 

5.9 

11.8 

82.4 


8 

4 

6 

18 


22.2 
11.1 
16.7 
50.0 


51 
9 

4 
17 


63.0 

11.1 

4.9 

21.0 


59 
14 
12 
49 


44.0 

10.4 

9.0 

36.6 


2.11* 

.61 

.47 

ND 


4.07** 




ND 
2.09* 




ND 


Total specified.... 


17 


100.0 


36 


[ 100.0 


81 


100.0 


134 


100.0 






Unspecif ied-unknown- 


17 

4 


81.0 
19.0 


36 
29 


55.4 
44.6 


81 
45 


64.3 
35.7 


134 
78 


63.2 
36.8 










21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 









ND Not determined. 
Significant at 5-pct level. 



Significant at 1-pct level. 



The reporting mechanism did not permit the classification of fires into three sep- 



arate categories. 

fires, changes in the reporting mechanism 
for the "Unspecified," "None," and "Un- 
known" categories make it impossible to 
obtain a separate fire count for each 
category. The combination of these three 
categories comprises a major portion of 
the total fires for all the time periods. 
Where equipment is involved, in recent 
time periods, more fires were associated 
with the mobile equipment type. 

Means of Detection 

Means of fire detection appear in table 
35. In the most recent time period, the 
means of detection was not specified for 
a large portion (21.4 pet) of the fires, 
thus raising some questions as to the 
completeness of the data. Of the spe- 
cified means of detection, almost all 
were operators and/or workers. The 



relative frequency of fires discovered 
immediately increased while that of fires 
not immediately discovered decreased. 
This is further substantiated by the next 
table, which classifies fires by dura- 
tion. Hence, either operators and work- 
ers were becoming incresingly aware of 
fires and discovering them at an early 
stage, or for some reason there were more 
fires under 30 min being reported in the 
most recent time period. 

Duration 

Duration of surface fires appears in 
table 36. Duration is not specified for 
a large portion of fires for all the pe- 
riods; the analysis of this table is thus 
limited to those fires where the duration 
is specified. As there were too few spe- 
cified fires in the period 1950-67, a 



30 



TABLE 35. - Reported surface fires by means of detection, three time periods 





Per 


iod I 


Period II 


Period III 


Total 


It| 


Means of detection 


1950- 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 


Operator-worker 
Workers (not 


7 

8 

4 


36.8 

42.1 
21.1 


29 

26 

7 


46.8 

41.9 
11.3 


84 

12 
3 


84.8 

12.1 
3.0 


120 

46 
14 


66.7 

25.6 
7.8 


0.76 

ND 

ND 


5.14** 
4.33** 




ND 






Total specified.... 


19 


100.0 


62 


100.0 


99 


100.0 


180 


100.0 








19 
2 


90.5 
9.5 


62 
3 


95.4 
4.6 


99 
27 


78.6 
21.4 


180 
32 


84.9 
15.1 










21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 




.. ..... — ... . ... _.. . — j 

ND Not determined. 


*Sign 


ificant 


at 1 


-pet level. 













TABLE 36. - Reported surface fires by duration, three time periods 





Per 


iod I 


Period II 


Period III 


Total 


It| 


Duration, h 


1950-67 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 


to 0.5 


3 

1 
3 
4 



27.3 

9.1 

27.3 

36.4 

.0 


16 

10 
8 
2 
3 


41.0 

25.6 

20.5 

5.1 

7.7 


29 

10 

6 

2 

2 


59.2 

20.4 

12.2 

4.1 

4.1 


48 

21 

17 

8 

5 


48.5 

21.2 

17.2 

8.1 

5.1 


0.83 
1.17 

.84 
2.81** 

.95 


1.69* 


0.5 to 1 


.58 


1+ to 4 


1.05 


4+ to 24 


ND 


24 + 


.73 






Total specified. ... 


11 


100.0 


39 


100.0 


49 


100.0 


99 


100.0 






Specified 


11 

10 


52.4 
47.6 


39 
26 


60.0 
40.0 


49 
77 


38.9 
61.1 


99 
113 


46.7 
53.3 














21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 










ND 


* * 

16.51 


51.51** 







Significant at 5-pct level. 



Significant at 1-pct level. 



chi-square test was not performed. For 
the remaining two time periods, the num- 
ber of fires is not evenly distributed 
across the fire duration categories. As 
mentioned previously, the relative fre- 
quency of fires under 30 min has in- 
creased in recent times. Also, the pro- 
portion of fires was significantly down 
in the 4- to 24-h category between 1950- 
67 and 1968-77. 

Number of Injuries 

Table 37 shows surface fires by number 
of injuries for the three time periods. 
In the first two time periods, approxi- 
mately 85 pet of the fires involved no 
injuries, whereas in the most recent time 
period, this was true for only about 45 
pet of the cases. In recent times there 



has definitely been a substantial in- 
crease in the proportion of fires being 
reported with one injury. This means ei- 
ther more workers have been sustaining 
fire injuries or changes in law and/or 
attitude have occurred that are affecting 
the reporting; that is, injuries that 
were previously not reported were being 
reported in the most recent time period. 

Number of Deaths 

Table 38 contains fires by number of 
deaths. The only significant result, 
fortunately, is the overall reporting 
frequency of nonfatal fires. Once the 
nonfatal fires are removed, the only re- 
maining category is fires involving one 
death. 



31 



TABLE 37. - Reported surface fires by number of injuries, three time periods 





Per 


iod I 


Period II 


Peri 


od III 


Total 


It| 


Number of injuries 


1950-67 


1968-77 


1978-84 


No. 


Pct 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 





18 
2 

1 




85.7 
9.5 

.0 
4.8 

.0 


54 
7 
4 




83.1 

10.8 

6.2 

.0 

.0 


56 

65 

4 

1 




44.4 

51.6 

3.2 

.8 

.0 


128 

74 

8 

2 




60.4 

34.9 

3.8 

.9 

.0 


ND 
ND 
ND 
ND 
ND 


5.12** 


1 


5.51 ** 


2 to 5 


ND 

ND 
ND 




21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 


NAp 


NAp 


NAp Not applicable. 


ND Not determined. 


Significant 


at 1- 


pet level. 





TABLE 38. - Reported surface fires by number of deaths, 
three time periods 



Number o 


f deaths 


1950-67 


1968-77 


1978-84 


Total 




No. 


Pet 


No. 


Pet 


No. 


Pet 


No. 


Pet 





18 
3 



85.7 

14.3 

.0 


59 
6 



90.8 

9.2 

.0 


123 
3 



97.6 

2.4 

.0 


200 

12 




94.3 


1 


5.7 


2 + 


.0 










21 


100.0 


65 


100.0 


126 


100.0 


212 


100.0 



TABLE 39. - Reported surface fires by successful extinguishing agent, 1 
three time periods 





Period I 


Peri 


od II 


Period III 


Total 


It| 


Extinguishing agent 


1950-67 


1968-77 


1978-84 


No. 


Pet 


I vs. 
II 


II vs. 




No. 


Pet 


No. 


Pet 


No. 


Pet 


Ill 




10 
9 
1 
2 


45.5 

40.9 

4.5 

9.1 


29 

11 

10 

9 


49.2 
18.6 
16.9 
15.3 


14 
4 
6 
4 


50.0 
14.3 
21.4 
14.3 


53 

24 
17 
15 


48.6 
22.0 
15.6 
13.8 


ND 
2.07* 
1.45 

ND 


ND 




ND 




0.50 




ND 


Total specified. . . . 


22 


100.0 


lJ9 


100.0 


28 


100.0 


109 


100.0 








22 
2 


91.7 
8.3 


59 
11 


84.3 
15.7 


28 
100 


21.9 
78.1 


109 
113 


49.1 
50.9 




Total 1 


24 
21 


100.0 
NAp 


70 
65 


100.0 
NAp 


128 
126 


100.0 
NAp 


222 
212 


100.0 
NAp 










11.82 


18.49** 


9.71* 









ND Not determined. 
Significant at 5-pct level. 



Significant at 1-pct level, 
^ore than 1 successful extinguishing agent used in some fires. 



Successful Extinguishing Agent agent 

(100/ 

Table 39 gives the frequency with which speci 

an extinguishing agent was successfully five, 

used in each of the three time periods. perio 

The fires in which two agents were sue- tingu 

cessfully used were entered under both these 

categories in this table. In period table 

1978-84, the successful extinguishing manne 



was not specified in about 80 pet 

126) of the reported fires. Of the 

fied fires, there were only three, 

and two fires, respectively, in 

ds I, II, and III that used two ex- 

ishing agents successfully. Since 

members are relatively small, this 

is not analyzed in the same 

r as its counterpart table 23 on 



32 



underground fires. Instead, the standard 
tests were performed. The data show wa- 
ter to be consistently successful in 
about 50 pet of the specified fires for 
all three periods. The burned-out method 
has been used less frequently since 1968. 

COMPARISON OF UNDERGROUND 
AND SURFACE FIRES 

Time Trends 



Ignition Source 

Electrical equipment was the leading 
ignition source of undergropund fires. 
For surface fires, engine heat was the 
leading ignition source, followed by 
electrical equipment (tables 7 and 31). 
For both underground and surface, the 
proportion of electrical fires decreased 
while the proportion of engine heat fires 
increased between 1968-77 and 1978-84. 



Although the total number of fire inci- 
dents was approximately the same for un- 
derground and surface, the distribution 
of these incidents across the three time 
periods was more variable for surface 
than for underground (fig. 2). The aver- 
age number of surface fires per year for 
which a report could be located ranged 
from 1.2 in 1950-67 to 18.0 in 1978-84. 
For underground fires the range was from 
3.4 to 10.9. Figure 2 also shows that 
for the most recent time period there 
were, on the average, 18.0 surface fires 
reported per year versus 10.9 for under- 
ground. Hence, it would appear that in 
the recent time period the surface area 
is more hazardous than the underground 
area. However, this is not the case, as 
can be seen from figure 3. This is be- 
cause many more hours were worked in the 
surface area than in the underground 
area. Figure 3 also shows 1978 to be the 
most hazardous year. 



Burning Substance 

As indicated in tables 8 and 32, more 
than one substance was burning in many 
fires. Combustible liquids were the pre- 
dominant burning substance for both un- 
derground and surface fires in the period 
1978-84. Also, the relative frequency of 
fires involving combustible liquids in- 
creased from one period to the next for 
both underground and surface fires. The 
proportion of fires involving timber, on 
the other hand, dropped sharply between 
1950-67 and 1968-77. 

Location 

Since the major categories for location 
(tables 9 and 33) differ vastly for un- 
derground and surface fires, they are not 
compared. 

Equipment Involved 



Ore Type 

Of the major ore types, copper and iron 
were the only ones involved in both un- 
derground fires and surface fires. Over 
the entire period, copper was the princi- 
pal ore involved in underground fires and 
was third in surface fires. Of the spe- 
cified ore types, copper accounted for 
about 18.0 pet of the underground fires 
and 8.6 pet of the surface fires (tables 
5 and 29) . In terms of incidence rates 
for the 1978-84 period, it ranks low for 
both underground and surface fires (fig- 
ures 4 and 6). 



The predominant equipment involved in 
both underground and surface fires was of 
the mobile type. Figure 7 shows a com- 
parison of mobile equipment fires in 
surface and underground mines over the 
three time periods. The relative fre- 
quency of fires involving this equipment 
type increased from one period to the 
next for both surface and underground 
fires. 

Means of Detection 

Most fires incidents were detected by 
the operators and/or workers, both in 



33 



u 

Q 



20 - 



KEY 



Underground 






1950-67 1968-77 1978-84 

Figure 7. — Percentage of mobile equipment fires, underground versus surface, during three time periods. 



surface and underground. Also, data in 
tables 14 and 35 show that, on the whole, 
the proportion of fires discovered 
immediately increased with each time 
period (fig. 8). 

Duration 



For the period 1950-67, about 55 pet of 
the reported underground fires lasted 
longer than 24 h. There were no surface 
fires reported in this category for the 
same period (tables 15 and 36). The per- 
centage of underground fires reported in 
the 0- to 0.5-h category was approximate- 
ly the same across the three time peri- 
ods, while for surface fires there was 
definitely an increase between 1968-77 
and 1978-84. 



Number of Injuries 

As indicated by tables 17 and 37, the 
majority of underground and surface fires 
did not cause injuries. However, for the 
most recent time period, this was not 
true in the case of surface fires. In 
this case, only 44 pet of the fires had 
no injuries, 52 pet had one injury, and 
4 pet had two or more injuries. Also, 
for both underground and surface, there 
were no fires resulting in 10 or more 
injuries. 

Number of Deaths 

Both in underground and surface, ap- 
proximately 95 pet of the fires were non- 
fatal (tables 21 and 38). 



34 



r-. 90 



o 

** 80 



u 

Q 



50 - 



30 



20-- 



KEY 




Undaroround 



Surf aca 






1950-67 19BB-77 1978-84 

Figure 8. — Percentage of fires detected immediately, underground versus surface, during three time periods. 



Successful Extinguishing Agent 

As can be seen in tables 23 and 39, wa- 
ter was the predominant successful agent 
used to extinguish both underground and 



surface fires. Also, in both underground 
and surface fires, two extinguishing 
agents were successfully used in some of 
the fires. 



NONREPORTABLE FIRES 



Since 1968, MSHA regulations have re- 
quired that fires lasting 1/2 h or more 
or involving an injury must be reported. 
Each reported fire is investigated by an 
MSHA inspector who then prepares a fire 
report. Noninjury fires under 1/2-h dur- 
ation are not reportable. 

To develop a data base that represented 
mine fires in general, 16 local and re- 
gional safety directors in charge of 12 



surface mines and 12 underground mines 
were interviewed to obtain descriptions 
of nonreportable fires at their mines 
over the last 5 yr. Internal company 
memos on these fires were also provided. 
Nonreportable data were analyzed in two 
sets: under the headings of underground 
fires and surface fires. A total of 20 
underground (table 40) and 22 surface 
(table 41) fire reports were obtained. 



35 



TABLE 40. - Nonrepor table underground fires 
(Based on sample of 20 reports) 



Ignition source: 

Electrical 

Welding 

Friction 

Engine heat 

Spontaneous combustion. 

Unspecified 

By burning substance: 1 

Combustible liquids.... 

Wiring insulation 

Timber 

Rubber hose 

By location: 

Haulageway-drif t 

Substation < 

Shaft 

Mined-out area 



Number 



10 
4 
3 
1 
1 
1 



By location — Con. 

Working face 

Other 

Unspecified 

By equipment involved: 

Mobile 

Electrical 

Maintenance-shop 

None 

Unspecified-unknown 

By successful extinguishing 
agent: 2 

Dry chemical 

Cut off electrical power. 

Water 

Seals 

Other 



*More than 1 burning substance involved in some fires. 

2 More than 1 successful extinguishing agent used in some fires. 

TABLE 41. - Nonreportable surface fires 
(Based on sample of 22 reports) 



Ignition source: 

Welding 

Electrical 

Engine heat , 

Friction , 

Other , 

Unspecified 

By burning substance: 1 
Combustible liquids.. 

Insulation , 

Rubber , 

Other , 

Unspecified 

By location: 

Surface 

Surface building. . . . 
Unspecified 



Number 

5 
4 
3 
2 
2 
6 

12 
3 
2 
4 
2 

14 
5 
3 



By equipment involved: 

Mobile 

Conveyor 

Electrical 

None 

Unspecified 

By successful extinguishing 
agent: 2 

Dry chemical 

Water 

Burned out 

Other 

Unspecified 



Number 

1 
1 
4 



15 

5 
4 
1 
2 



Number 

14 
2 
1 
1 
4 



13 
1 
1 
5 
3 



More than 1 burning substance involved in some fires. 
2 More than 1 successful extinguishing agent used in some fires. 



36 



UNDERGROUND FIRES 

Ignition Source 

Most of the nonreportable underground 
fires were electrical in origin, pri- 
marily from wiring shorts. The sec- 
ond highest ignition sources were weld- 
ing sparks or hot slag and friction, 
primarily from welding near combustibles 
and overheating brakes, respectively. 

Burning Substance 

Combustible liquids, wiring insulation, 
and timber were nearly equal in frequency 
of involvement. 

Location 



As with reported fires, the most fre- 
quent location of nonreportable fires was 
along haulageways and in drift entries 
where activity is high. Nonreportable 
fires also occurred with a relative high 
frequency at substations or switchboxes. 

Equipment Involved 

Unlike the reported fires, it was pos- 
sible to separate the fires which in- 
volved no equipment from those that were 
unspecified or unknown. Fires where no 
equipment was involved usually resulted 
from welding or cutting, where combusti- 
bles such as timber or grease and oil 
were ignited. Where equipment was in- 
volved, the most frequent type was mo- 
bile, as was the case with reported 
fires. 

Successful Extinguishing Agent 

Unlike the reported fires, the most 
frequently used agent here was one or 
more hand-portable dry chemical extin- 
guishers. Also, water and the local 



removal of electric power were used with 
relative frequency. 

SURFACE FIRES 

Ignition Source 

Welding, electrical, and engine heat 
were frequently cited as ignition 
sources. Welding sparks can ignite 
grease or oil that has accumulated on 
vehicles. Electrical fires are generally 
from wiring shorts that ignite diesel 
fuel or hydraulic fluid. Engine heat can 
ignite hydraulic fluid or diesel fuel 
from a ruptured line. 

Burning Substances 

As with reported fires, combustible 
liquids were most frequently involved. 

Location 

Most surface fires occurred along haul- 
age roads or in the pit area on mobile 
machinery. 

Equipment Involved 

An overwhelming majority of nonreport- 
able surface fires involved mobile ma- 
chinery such as haulage trucks, front-end 
loaders, and flatbed welding trucks. 
These findings are consistent with those 
from fires that were reported. 

Successful Extinguishing Agent 

Most of these fires were extinguished 
by hand-portable dry chemical extin- 
guishers and one automatic fire suppres- 
sion system. This finding is quite dif- 
ferent from that for reported fires where 
water is consistently the most success- 
ful extinguishing agent used. 



OPINION DATA FROM MINE SAFETY DIRECTORS 



When gathering data on rare events such 
as fires, it is often advisable to ask 
knowledgeable individuals to give hazard 
opinion data. Consequently, after the 



mine safety directors related their non- 
reportable fire data, they were asked to 
rank various ignition sources, burning 
substances, successful extinguishing 



37 



agents, and equipment on their relative 
frequencies of occurrence in nonreport- 
able fires. Because of the size of the 
opinion data sample, it is difficult to 
specify with any certainty the reliabil- 
ity. These data are presented as a sam- 
ple of the metal and nonmetal fire ex- 
perience of the group of mine safety 
personnel. 

UNDERGROUND MINE FIRES 

Table 42 contains ranked opinions of 
ignition sources, burning substances, and 
successful extinguishing agents for un- 
derground nonreportable fires. Each item 
is listed according to the average rank 
assigned to it by the safety direc- 
tors interviewed. The top three ignition 
sources were welding sparks or hot slag, 
electrical arcing, and friction. The top 
two burning substances were combustible 
liquids and insulation. The top two suc- 
cessful extinguishing agents were dry 
chemicals and water. 



SURFACE MINE FIRES 

Table 43 contains ignition sources, 
burning substances, and successful extin- 
guishing agents for surface nonreportable 
fires. Each item is listed according to 
the average rank assigned to it by the 
safety directors interviewed. The top 
three ignition sources were welding 
sparks or slag, engine heat, and elec- 
trical arcing. The top two burning sub- 
stances were combustible liquids and 
rubber. The top two successful extin- 
guishing agents again were dry chemicals 
and water. 

SUMMARY OF OPINION DATA 

After the safety directors were inter- 
viewed concerning nonreportable fires, a 
consensus of general opinions became ap- 
parent. The primary causes of nonreport- 
able underground fires were poor mainte- 
nance of electrical equipment and poor 
housekeeping, coupled with a lack of 



TABLE 42. - Average rankings of opinion data for ignition source, 
burning substance, and successful extinguishing agent, 
underground fires 



Rank 


Ignition source 


Rank 


Burning substance 


Rank 


Extinguishing agent 


1... 


Welding sparks or 


1... 


Combustible liquids. 


1... 


Dry chemical. 




slag. 


2... 


Wiring insulation. 


2... 


Water. 


2... 


Electrical. 


3... 


Rubber (hose or 


3... 


Other. 


3... 


Friction. 




belt). 






4... 


Engine heat. 


4... 


Timber, lagging, 






5... 


Spontaneous 




etc. 








combustion. 


5... 


Other. 






6... 


Other. 











TABLE 43. - Average rankings of opinion data for ignition source, 
burning substance, and successful extinguishing agent, 
surface fires 



Rank 


Ignition source 


Rank 


Burning substance 


Rank 


Extinguishing agent 


1... 


Welding sparks or 


1... 


Combustible liquids. 


1... 


Dry chemical. 




slag. 


2... 


Rubber (hose or 


2... 


Water. 


2... 


Engine heat. 




belt). 


3... 


Other. 


3... 


Electrical. 


3... 


Insulation. 






4... 


Spontaneous 


4... 


Other. 








combustion. 


5... 


Timber, lagging, 






5... 


Other. 




etc. 







38 



caution on the part of welders when work- 
ing near combustibles. Welding on under- 
ground mining machinery frequently in- 
volves the spot ignition of combustibles 
that accumulate on this equipment. The 
primary causes of nonreportable surface 
fires were poor equipment design, poor 
maintenance, and poor housekeeping. The 
routing of fluid lines on surface mining 
equipment was frequently cited as con- 
tributing to an increased fire hazard. 



Several safety directors mentioned ef- 
forts undertaken at their mines to re- 
route or shield these lines from the ig- 
nition sources of electrical arcing and 
engine heat. Leaks of hydraulic fluid, 
oil, and other lubricants frequently col- 
lect in hard-to-reach locations. These 
substances eventually are ignited by a 
cutting torch, electrical arc, or engine 
heat. 



SUMMARY 



Major findings of the study appear 
in tables 44 and 45. The most frequent 
ignition sources, burning substances, 
eqiupment types, locations, and success- 
ful extinguishing agents of reported and 
nonreportable fires are discussed below. 

IGNITION SOURCE 

The majority of underground mine fires, 
both reported and nonreportable, were 



electrical. Electrical equipment was al- 
so the primary cause of underground fires 
resulting in injuries during the period 
1950-84. In recent times, however, en- 
gine heat has become the leading cause of 
fires resulting in injuries. Engine heat 
was the leading ignition source for re- 
ported surface fires, and welding for 
nonreportable surface fires. 



TABLE 44. - Major study findings of reported fires 
(Factors listed in sequence of significance) 



Category 



1950-77 



1978-84 



Total 





UNDERGROUND 




Ignition source. . 


Electrical, welding. . 


Electrical, engine 


Electrical, welding, 






heat. 


engine heat. 


Burning substance 


Timber, insulation, 


Combustible liquids, 


Timber, combustible 




combustible liquids. 


timber, insulation. 


liquids, insulation. 




Haulageway-drif t , 
shaft-raise-winze. 


Haulageway-drif t, 
shaft-raise-winze. 


Haulageway-drif t, 
shaft-raise-winze. 




Equipment 


Mobile, electrical.. 


Mobile, electrical.. 


Mobile, electrical. 


involved. 








Successful extin- 


Water, dry chemical. 


Water, dry chemical. 


Water, dry chemical. 


guishing agent. 








SURFACE 


Ignition source. . 


Electrical, welding, 


Engine heat, weld- 


Engine heat, electri- 




engine heat. 


ing, electrical. 


cal, welding. 


Burning substance 


Combustible liquids, 


Combustible liquids, 


Combustible liquids, 




construction 


construction 


Construction 




material. 


material. 


materials. 








Surface building, 
surface. 




building. 


Equipment 


Mobile, electrical... 


Mobile, conveyor.... 


Mobile, conveyor, 


involved. 






electrical. 


Successful extin- 


Water, burned out.... 


Water, dry chemical. 


Water, burned out. 


guishing agent. 









39 



TABLE 45. - Major study findings of nonreportable fires 
(Factors listed in sequence of significance) 



Category 



Underground 



Surface 





NONREPORTABLE FIRES 






Combustible liquids, wiring insula- 
tion, timber. 

Mobile, electrical, maintenance-shop 
Dry chemical, cut off electrical 
power, water. 


Welding, electrical, 

engine heat. 
Combustibles liquids, 

insulation. 




Successful extinguishing 
agent. 


building. 
Mobile. 
Dry chemical. 



OPINION DATA 







Welding, engine heat. 
Combustible liquids, 




Combustible liquids, wiring 




insulation. 


rubber (hose or 
belt). 


Successful extinguishing 
agent. 




Dry chemical, water. 





BURNING SUBSTANCE 

The most frequent burning substance in 
reported underground fires was timber, 
followed by combustible liquids and in- 
sulation. In nonreportable underground 
fires, combustible liquids, wiring insu- 
lation, and timber were involved with 
about equal frequency. For reported sur- 
face fires, the most frequent burning 
substance was combustible liquids, fol- 
lowed by construction material. In non- 
reportable surface fires, combustible 
liquids were most frequently involved. 

LOCATION 

Reported underground fires occurred 
along haulageways or in drift entries 
where electrical and diesel equipment are 
concentrated. Nonreportable fires also 
occurred at these locations more fre- 
quently than at any other. 

Reported surface fires occurred primar- 
ily in mill buildings, and nonreportable 
surface fires occurred primarily on mo- 
bile equipment along haulage roads or in 
the pit area. In recent times, however, 
the reported surface fire locations were 
about evenly split between surface build- 
ing and surface area other than building. 



EQUIPMENT INVOLVED 

The equipment most frequently involved 
in reported and nonreportable underground 
and surface fires is the mobile type such 
as load-haul-dumps. These vehicle fires 
are more quickly detected and are extin- 
guished with hand-portable extinguishers 
since there is less structure to collect 
smoke or otherwise conceal the fire. 

SUCCESSFUL EXTINGUISHING AGENT 

The most frequently successful extin- 
guishing agent for reported fires was wa- 
ter. For nonreportable fires, dry chemi- 
cal hand-portable fire extinguishers were 
used most often. This Is consistent with 
the duration of reportable fires. The 
first attack on a fire is generally with 
a hand-portable extinguisher. If the at- 
tempt is successful, then the fire is 
most likely extinguished at the nonre- 
portable stage. If the fire has grown in 
size, or initial extinguishing attempts 
prove unsuccessful, then the fire will 
probably become reportable while water is 
brought to the area and applied to the 
fire. 



40 



CONCLUSIONS 



Fire incidence rates in both surface 
and underground mines are not declining. 
Despite the considerable efforts of mine 
safety personnel, regulatory action, and 
fire safety-related research, little 
progress toward reducing the incidence of 
fire in recent years (1978-84) is appar- 
ent. One possible explanation, which is 
supported to some extent by the data on 
ignition sources, burning substances, and 
equipment involved, is that fire hazards 
are changing as mining methods, mate- 
rials, and equipment evolve. As specific 
fire hazards are recognized and cor- 
rected, new mining technology introduces 
other hazards into the workplace. This 
explanation suggests that the present 
level of fire safety effort may not suc- 
ceed in reducing fire incidence rates, 
and that an accelerated pace of activity 
with particular focus on newly emerging 
mining technologies is required if inci- 
dence rates are to be reduced. 



Conclusions regarding the relative im- 
portance of a given fire hazard for one 
time period do not necessarily hold for 
subsequent periods, suggesting the value 
of regular updates to the fire incident 
data base. Timely collection, analysis, 
and publication of such data will help 
ensure that fire safety efforts will ad- 
dress the greatest needs. 

Finally, the depth and breadth of the 
data contained in this report is signifi- 
cant in itself. The level of detail pro- 
vided will enable users to concentrate 
their efforts on the research instead of 
on collecting data, thereby maximizing 
effectiveness. The relative hazardous- 
ness of various equipment and procedures 
has been presented in clear and concise 
fashion. The data were put on a floppy 
disk in the Lotus 1-2-3 format to facili- 
tate the analysis. Microdata are also 
available from the authors on hard copy. 



41 



MSHA fire reports for 1950 
spection offices: 

Northeastern District 

Northeastern District Office 
Pittsburgh, PA 15213 

Pittsburgh Subdistrict Office 
Pittsburgh, PA 15213 

Albany Subdistrict Office 
Albany, NY 12201 

Southeastern District 

Southeastern District Office 
Birmingham, AL 35209 

Birmingham Subdistrict Office 
Birmingham, AL 35209 

Knoxville Subdistrict Office 
Knoxville, TN 37902 

North Central District 

North Central District Office 
Duluth, MN 55802 

Duluth Subdistrict Office 
Duluth, MN 55802 

Vincennes Subdistrict Office 
Vincennes, IN 47591 



APPENDIX 
through 1977 were acquired from the following MSHA in- 
South Central District 



South Central District Office 
Dallas, XX 75209 

Dallas Subdistrict Office 
Dallas, TX 75209 

Rolla Subdistrict Office 
Rolla, MO 65401 

Rocky Mountain District 

Rocky Mountain District Office 
Denver, CO 80225 

Denver Subdistrict Office 
Denver, CO 80225 

Salt Lake City Subdistrict Office 
Salt Lake City, UT 84115 

Western District 

Western District Office 
Alameda, CA 94501 

Bellevue Subdistrict Office 
Bellevue, WA 98004 

Phoenix Subdistrict Office 
Phoenix, AZ 85004 



INT.-BU.0F MINES,PGH.,PA. 28451 



U.S. GOVERNMENT PRINTING OFFICE: 1987 - 605-017/60007 



W84 



U.S. Department of the Interior 
Bureau of Mines— Prod, end Dtstr. 
Cochrens Mill Road 
P.O. Box 18070 
Pittsburgh. Pe. 15236 



OFFICIAL BUSINESS 
PENALTY FOR PRIVATE USE, S300 

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